Error rate in five-state myoelectric control systems

A myoelectric control system is one in which the operation of a device is controlled by the electric potential produced by voluntary contraction of a muscle. The utilisation of a single muscle site for the 3-state control of a myoelectric prosthesis has proven beneficial for certain amputees. It has been proposed that a single muscle site could be used for 5-state control, perhaps for an elbow and hand. This paper presents a preliminary study of the error probability for 5-state control.     

Smart orthosis for the treatment of adolescent idiopathic scoliosis

There is considerable controversy regarding the effectiveness of orthotic treatment for patients with adolescent idiopathic scoliosis. Most researchers believe that, to be effective, the orthosis must be worn as prescribed for both compliance and tightness. Compliance is the time the brace is worn relative to the prescribed time. A battery-powered microcomputer system was developed to monitor and maintain the loads exerted by orthoses used to treat children with spinal deformities during daily living. This system not only records how well and for how much time the brace has been used, but also helps patients to ensure that the brace is being worn at the prescribed tightness. Laboratory tests were performed, and five patients used the system for four weeks. The patients reported that the system helped them to wear the orthoses correctly and comfortably. The time that the patients wore the orthoses at the prescribed tightness level increased from 53±9% during the monitoring period (first 2 weeks) to 68±14% during the automatic adjustment period (last 2 weeks).     

Differentiation of mammalian skeletal muscle cells cultured on microcarrier beads in a rotating cell culture system

The growth and repair of adult skeletal muscle are due in part to activation of muscle precursor cells, commonly known as satellite cells or myoblasts. These cells are responsive to a variety of environmental cues, including mechanical stimuli. The overall goal of the research is to examine the role of mechanical signalling mechanisms in muscle growth and plasticity through utilisation of cell culture systems where other potential signalling pathways (i.e. chemical and electrical stimuli) are controlled. To explore the effects of decreased mechanical loading on muscle differentiation, mammalian myoblasts are cultured in a bioreactor (rotating cell culture system), a model that has been utilised to simulate microgravity. C₂C₁₂ murine myoblasts are cultured on microcarrier beads in a bioreactor and followed throughout differentiation as they form a network of multinucleated myotubes. In comparison with three-dimensional control cultures that consist of bioreactor exhibit an attenuation in differentiation. This is demonstrated by reduced immunohistochemical staining for myogenin and α-actinin. Western analysis shows a decrease, in bioreactor cultures compared with control cultures, in levels of the contractile proteins myosin (47% decrease, p<0.01) and tropomyosin (63% decrease, p<0.01). Hydrodynamic measurements indicate that the decrease in differentiation may be due, at least in part, to fluid stresses acting on the myotubes. In addition, constraints on aggregate size imposed by the action of fluid forces in the bioreactor affect differentation. These results may have implications for muscle growth and repair during spaceflight.     

Role of guanylate cyclase and arachidonic acid metabolites in the regulation of epithelium-dependent relaxation of tracheal smooth muscles in rats

The effects of guanylate cyclase modulators and inhibitors of the arachidonic acid metabolism on epithelium-dependent smooth muscle reactions of rat tracheal segments were studied by a mechanographic technique. Application of phenylephrine to the tracheal segments precontracted by high-potassium Krebs' solution reduced their mechanical tension. This reaction was considerably less pronounced in the tracheal segments from which the epithelium had been removed. Phenylephrine-induced relaxation was suppressed by preincubation with methylene blue, but was not affected by preincubation with either indomethacin (a cyclooxygenase inhibitor) or nordihydroguaiaretic acid (a lipoxygenase inhibitor). These data suggest that the epithelium-dependent relaxation of the tracheal smooth muscle is mediated by guanylate cyclase activation, and arachidonic acid metabolites do not significantly contribute to this reaction. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 127, No. 1, pp. 9–11, January 1999     

The early onset of maximum velocity of shortening in heart muscle of the cat

Summary The time at which the contractile elements (CE) of heart muscle are capable of shortening with maximum velocity at zero load (V _max) has been derived from isotonic contractions at increasing afterloads in the papillary muscle of the cat. The time interval from the stimulation to peak velocity of shortening of isotonic contractions at increasing afterloads was found to be a linear function of load with a highly significant correlation (r>0.99). Thus, the intercept of this function with the time axis at zero load provides an estimate of the time of the onset ofV _max. It has been calculated that theV _max sets in very early during the course of the contraction at only 20% of the time from stimulation to peak isometric tension both in control conditions and following various inotropic interventions. Thus in heart muscle the early ability of the CE to shorten with maximum velocity at zero load (V _max) has to be dissociated from the course of the active state in terms of force resistance to stretch.     

Development of a model system for evaluation of human endothelial cell proliferationin Vitro: Possible clinical applications

A system for evaluation of the ability of human blood serum to affect endothelial cell proliferation was developed and tested. The system based on incorporation of³H-thymidine into DNA was used to analyze the effects of hormone replacement therapy on endothelial repair and angiogenesis. Blood serum from 12 menopausal women less effectively activated endothelial proliferation compared to control donor serum. After 6-month hormone replacement therapy with Divina (a combination of estradiol and medroxyprogesterone), this index increased in seven female subjects (58.3%), but remained below the control level. The model proposed by us can be used in clinical practice and drug testing for evaluation of the influence of blood serum on vascular endothelium. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 129, No. 4, pp. 404–407, April, 2000     

Model determination for use in automated control of drug dosages: application to d-tubocurarine

To implement a feedback control system to achieve satisfactory muscle relaxation during surgical procedures, a mathematical formalism, based on linear compartmental theory, is derived to model the input/output response between the dosage of a drug administered and its neuromuscular effect as measured by the train-of-four (T4) ratio twitch response. The effect (T4 ratio) is related directly to the dosage schedule, and no attempt is made to include the plasma concentration of the neuromuscular blocking drug in the formalism. The neuromuscular blocking data of 24 patients, in whom the muscle relaxant d-tubocurarine (curare) was used, were fitted using a nonlinear least-squares data fitting routine. The number of compartments necessary to fit the data for each patient was determined using the general linear test. In all but three cases a biexponential model was sufficient to fit the data. Simulation studies also show that a biexponential model gives satisfactory control even for those patients for whom a triexponential model was necessary to fit the data. Further simulation shows that because of interindividual variation the application of adaptive control techniques will be needed.     

Effect of early fasciotomy on intramuscular pressure and electrical excitability of muscles in experimental compartment syndrome

Experiments on rabbits with compartment syndrome of the leg showed that the main pathogenetic factors of muscle injury are postischemic contracture leading to extravascular microcirculatory disorders and tissue necrosis(early postcompression period) and progressive subfascial edema (18 h-4 days). Therapeutic effect of fasciotomy in the early period consists in restoration of bloodflow due to relaxation of contracted muscles and in the late period in decompression of edematous muscles and prevention of secondary ischemia. Fasciotomy through a small section does not lead to sufficient relaxation of rigid muscles and does not essentially increase the subfascial volume. Fasciotomy decreases subfascial pressure and muscle excitability threshold, however they remain considerably elevated during day 1. An electrodiagnostic test is proposed for early (before subfascial edema) detection of postischemic contracture. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 130, No. 9, pp. 284–288, September, 2000     

Effect of early fasciotomy on intramuscular pressure and electrical excitability of muscles in experimental compartment syndrome

Experiments on rabbits with compartment syndrome of the leg showed that the main pathogenetic factors of muscle injury are postischemic contracture leading to extravascular microcirculatory disorders and tissue necrosis(early postcompression period) and progressive subfascial edema (18 h-4 days). Therapeutic effect of fasciotomy in the early period consists in restoration of bloodflow due to relaxation of contracted muscles and in the late period in decompression of edematous muscles and prevention of secondary ischemia. Fasciotomy through a small section does not lead to sufficient relaxation of rigid muscles and does not essentially increase the subfascial volume. Fasciotomy decreases subfascial pressure and muscle excitability threshold, however they remain considerably elevated during day 1. An electrodiagnostic test is proposed for early (before subfascial edema) detection of postischemic contracture. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 130, No. 9, pp. 284–288, September, 2000     

Peculiarities of the effect of parathyroid hormone on the relaxation of rat myocardium

Contraction of rat myocardium is recorded in a regime of physiological loading that simulates the function of the intact myocardium. Addition of parathyroid hormone accelerates relaxation of the rat myocardium in the control solution and in a solution containing norepinephrine or high calcium concentrations. In a regime of isometric loading the addition of parathyroid hormone inhibits relaxation. At a low Ca concentration in the medium, parathyroid hormone has no effect on the rate of relaxation. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 121, No. 4, pp. 410–413, April, 1996 Presented by A. N. Klimov, Member of the Russian Academy of Medical Sciences     

Biokinetics of transdermal therapeutic medicinal form of phenazepam

We studied the rate of phenazepam absorption into the blood and its transport to the brain from a transdermal therapeutic system and bioavailability of the drug in this system. Hydrogel matrix consisting of polyvinyl alcohol and 1,2-propylene glycol was used for application. Transdermal application of 0.1–0.4 mg phenazepam in a dose of 14 mg/kg provided a stable level of this drug during application interval (1–48 h), while its bioavailability for blood plasma and brain was 0.63 and 0.2, respectively (determined for 0.4 mg phenazepam). The rate of drug penetration into the blood and brain was 46 and 60 ng/ml/h, respectively. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 130, No. 12, pp. 633–635, December, 2000     

The role of intracellular Ca2+ pool in sodium nitroprusside-induced relaxation of rat aorta smooth muscle cells

A relaxation effect of sodium nitroprusside on smooth muscle cells of rat aorta due to intracellular Ca²⁺-store refilling is demonstrated using the double sucrose gap technique. It is suggested that sodium nitroprusside-induced repolarization of the smooth muscle cell membrane is associated with inhibition of Ca permeability and/or Ca-dependent K⁺ permeability of the plasma membrane. Translated fromByulleten' Eksperimental'noi Biologii I Meditsiny, Vol. 127, No. 2, pp. 177–179, February 1999     

Intramuscular pressures during exercise: an evaluation of a fiber optic transducer-tipped catheter system

Summary The efficacy of a modified fibre optic transducer-tipped catheter system for measuring intramuscular pressures during exercise was determined. A microcapillary infusion technique using a catheter was employed as the standard of comparison due to its established dynamic properties. Pressures were measured in the tibialis anterior muscle of six healthy adults at rest before exercise, during isometric and concentric exercise, and at rest after exercise. The fibre optic system measured contraction pressures equal to the microcapillary infusion technique during all phases of the exercise protocols but recorded a lower relaxation pressure during isometric exercise and a lower rest pressure following 20 min of concentric exercise. Negative relaxation pressures were recorded by the fibre optic system for two subjects during continuous concentric exercise. It is hypothesized that a piston effect, due to the sliding of muscle fibres at the catheter tip following a contraction, rendered falsely low pressures during relaxation and that this artefact was reflected in the subsequent rest pressure following exercise. The larger volume (157 mm³) and area (3.49 mm²) of the fibre optic catheter in the muscle made it more prone to this effect than the conventional catheter (39 mm³ and 0.87 mm², respectively). The fibre optic system may be preferred when recording the musclecontraction pressures during complex limb movements but should not be used when assessing the relaxation pressures or the pressure at rest following exercise.This project was performed at the Division of Orthopaedics and Rehabilitation, Veterans Administration Medical Center and the University of California San Diego     

Contractile and histochemical properties of regenerating cross-transplanted fast and slow muscles in the rat

Summary The soleus (SOL) or extensor digitorum longus (EDL) muscles of month-old rats were denervated for 14 days and then cross-transplanted so that the fast muscle was placed into the bed of the slow muscle and vice versa. At 17, 30, 60, and 90 days the transplants were tested for certain contractile and histochemical properties. By 90 days the cross-transplanted SOL showed complete conversion of the full contraction time and nearly complete conversion of the half relaxation time to those of the normal EDL. In contrast, the contraction and relaxation times of the cross-transplanted EDL became considerably slowed, but did not attain the values of the normal SOL. Histochemical staining for ATPase and SDH activity demonstrated similar transformations of fiber types. The degree of transformation of twitch and histochemical characteristics in cross-transplanted muscles was greater than the values reported after cross-innervation of the same muscles. The cross-transplantation model has certain advantages over nerve cross-union experiments because the cross-transplanted muscle is placed in the normal functional environment of the other muscle.Supported by grants from the Muscular Dystrophy Associations of America and a scientific exchange between the Academies of Sciences of Czechoslovakia and the United States.     

Precision,comfort and mechanical performance of the Quadriso-tester,a quadriceps force measuring device

The mechanical performance, repeatability and comfort of the Quadrisotester, which assesses isometric knee extensor muscle strength, were examined. Twenty healthy subjects and 20 patients treated for unilateral anteriorligamenta cruciata insufficiency were tested. Intra-rater repeatability was determined by the testing and retesting of subjects and calculation of the intra-class correlation coefficient and the mean difference between test and retest values. The comfort level was determined a questionnaire. Measuring time was recorded, and the relationship between knee angle and extension moment was plotted. Strength and stiffness were determined using the finite element method. Intra-rater repeatability was high; the intra-class correlation coefficient of the right and left leg was 0.90 and 0.91, respectively; the coefficient of variation was 6.4 and 6.0%, respectively. The median comfort score of the healthy subjects was 7, and that of the patients was 9. Measuring time remained within 30 min. Misalignment of the knee and sidebar axis disturbed the relationship between knee angle and extension moment. Strength and stiffness were higher than required. In conclusion, the Quadriso-tester is a comfortable and fast device to determine quadriceps force with a high repeatability. The knee and sidebar axis should be well aligned.     

Ultrastructure of the Miracidium of Echinostoma paraensei Lie and Basch, 1967 (Trematoda, Echinostomatidae)

The morphology of Echinostoma paraensei was studied using transmission electron microscopy. The terebratorium region has many electrondense secretory granules and many folds on the surface. The epidermal cells that cover the larval body have unique nuclear morphology, many mitochondria and vesicles being attached to the interepidermal ridges by a septate junction. The cilia present the organization 9+2 and a typical structure with a shaft, axosome, basal body and rootlet. Below the epidermal cells there is a layer of circular muscle and, adjacent to it, a layer of longitudinal muscle fibers. The excretory system has two flame cells, with internal and external ribs and leptotriches at the barrel region, an excretory vesicle and an excretory pore.     

Selective training-induced thigh muscles hypertrophy in professional road cyclists

Muscular adaptations linked to a high volume and intensity of training have been scarcely reported. We aimed at documenting, using MRI, the cross-sectional area changes associated with a high volume and intensity of training in 11 thigh muscles of a population of professional road cyclists as compared with sport science students. We were also interested in determining, whether selective muscle hypertrophy in professional road cyclists, if any, was correlated to selective exercise-induced T ₂ changes during a pedaling exercise on a cycloergometer. Cross-sectional area of 11 thigh muscles was quantified in sixteen subjects (i.e. eight professional road cyclists and eight sport science students) using MRI. In addition, transverse relaxation times (T ₂) were measured before and just after a maximal standardized constant-load exercise in order to investigate exercise-related T ₂ changes in these muscles. Professional road cyclists had a significantly higher relative amount of muscle (including the whole set of thigh muscles, 90.5±3.3%) as compared to controls (81.6±7.3%). Regarding relative values expressed with respect to the total thigh muscles CSA, Vastus lateralis and Biceps femoris CSA were significantly larger in cyclists whereas CSA of the Vastus intermedius was smaller. However, this selective hypertrophy was not correlated to the exercise-induced T ₂-increase. We have reported, for the first time, a selective hypertrophy of Vastus lateralis and Biceps femoris in professional road cyclists confirming their involvement in pedaling task and suggesting a possible cause–effect relationship between muscle activation and hypertrophy, associated with a specific pedaling skill.     

Role of motoneuron pulsed activity in the regulation of myosin composition in the slow skeletal muscle

The possible role of pulsed motoneuron activity in the regulation of the qualitative composition of the guinea pig slow skeletal muscle myosins is studied by immunohistochemical methods using monoclonal antibodies to the fast myosin heavy chains. Guinea pig intactmusculus soleus contains only the slow muscle fibers. Blockade of axon transport by colchicine application on the sciatic nerve during intact pulsation leads to the expression of fast myosin. Tenotomy simultaneous with the axon transport blockade prevents the appearance of the fast muscle fibers. Our results indicate that pulsed activity of motoneuron as a factor of neurotrophic control regulates the qualitative composition of myosins, thus supporting the functional activity of the muscle. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 126, No. 10, pp. 472–473, February 2, 1998     

Genetic control of muscle development: learning from Drosophila

Muscle development involves a complex sequence of time and spatially regulated cellular events leading to the formation of highly specialised syncytial muscle cells displaying a common feature, the capacity of contraction. Analyses of mechanisms controlling muscle development reveals that the main steps of muscle formation including myogenic determination, diversification of muscle precursors, myoblast fusion and terminal differentiation involve the actions of evolutionarily conserved genes. Thus dissecting the genetic control of muscle development in simple model organisms appears to be an attractive way to get insights into core genetic cascade that orchestrate myogenesis. In this respect, particularly insightful have been data generated using Drosophila as a model system. Notably, the interplay between intrinsic and extrinsic cues that determine the early myogenic decisions leading to the specification of muscle progenitors and those controlling myoblasts fusion are much better characterised in Drosophila than in vertebrate species. Also, adult Drosophila myogenesis, which leads to the formation of vertebrate-like multi-fibre muscles, emerges as a particularly well-adapted system to study normal and aberrant muscle development.     

Numerical modeling of ventricular filling

The fluid dynamical and physiological assumptions underlying general mathematical modeling of ventricular filling are outlined. We then describe the use of a lumped parameter model and computer simulation to study how the early transmitral velocity profile is affected by isolated changes in ventricular compliance and relaxation, atrial pressure and compliance, and valvular morphology. We show that the transmitral velocity is fundamentally affected by twophysical determinants: the transmitral pressure difference and the net compliance of the atrium and the ventricle. These physical determinants in turn are specified by the variousphysiologic parameters of interest. This approach has shown that peak velocity is most strongly affected by initial left atrial pressure, lowered somewhat by prolonged relaxation, low atrial and ventricular compliance, and systolic dysfunction. Peak acceleration is directly affected by atrial pressure and inversely affected by the time constant of isovolumic relaxation, with little influence of compliance, whereas the deceleration rate is almost purely given by mitral valve area divided by instantaneous atrioventricular compliance at the end of the rapid filling wave.