计算机辅助导航下膝关节置换术的手术配合

近年来随着计算机技术和空间示踪技术的发展与结合,计算机辅助导航手术系统受到临床广泛关注。计算机辅助导航系统可以准确、实时确定手术器械的位置和方向,从技术上为医生提供支援。     

Changes in physical functional capacity from 71 to 78 years of age for a population living at home. Data from a prospective study of an age cohort

ABSTRACT Retention of physical functional capacity is of great importance to the elderly for prospects of continuing life at home. Data are presented from a longitudinal population study of one whole age cohort consisting of elderly persons living at home. These people were examined at 71, 73, 76 and 78 years of age. Our intention was to elucidate changes in physical functional capacity occurring as age advanced. This capacity was evaluated according to the following parameters: primary ADL (activities of daily living), ability to use outdoor modes of transportation, mobility, balance and coordination, and walking indoors. The findings revealed generally good retained physical function in the age groups studied. Over 90% of all the elderly people in these groups could carry out primary ADL, could use some form of outside transportation, and had no problem walking indoors. By the criteria applied in this study, 23–33% of the people had impaired mobility. Legs were more troublesome than arms regarding mobility. It seems likely that living at home can provide daily exercise which is important in maintaining necessary physical function in daily life.     

Spatial learning and motor deficits in aged rats

Young (3 months) and aged (24 months) rats were compared on a range of behavioural tests. The aged animal were impaired in their acquisition of a spatial learining task in the Morris water maze, as well as showing deficits in motor coordination, swimming efficiency, and spontaneous locomotion and exploration in an open field. Qualitative observation and correlation analyses indicated that the aged group was heterogeneous in the degree of impairments manifested by the individual animals, and suggested that the development of impairments may progress with aging at different rates in the various tasks and possibly in different underlying neuroanatomical systems.     

International symposium on the brain-gut axis

Prostaglandin (PG) D₂ was studied to determine the pharmacological effects of this PG on the central nervous system. PGD₂ (0.45–4.05 mg/kg) decreased spontaneous locomotor activity in rats by as much as 66% of control, however, the neuromuscular coordination of mice, treated at the same doses of PGD₂, was not impaired. PGD₂ (0.05–4.05 mg/kg) also increased pentobarbital sleeping time in mice from 42% to 238% of control, in a dose-related manner. PGD₂ did not prevent convulsions induced in response to electroshock or pentylenetetrazol. Cats monitored for EEG responses to PGD₂ infusion displayed variable sensitivity to different doses (16–3000 μg) of drug, however, the characteristics response to PGD₂ was the conversion from a uniform low voltage, fast wave pattern to high voltage, show waves. Cats administered PGD₂ were sedated and sometimes catatonic, and displayed brief periods of hypotension, bradycardia, diarrhea, analgesia and hyperthermia at higher doses of the drug. Thus, PGD₂ possesses sedative properties in rodents and cats and may have a role in the central nervous system.     

Characterization of large conductance Ca2+-activated K+ channels in cerebellar Purkinje neurons

We investigated the role of large conductance, calcium-activated potassium channels (BK channels) in regulation of the excitability of cerebellar Purkinje neurons. Block of BK channels by iberiotoxin reduced the afterhyperpolarization of spontaneous action potentials in Purkinje neurons in acutely prepared cerebellar slices. To establish the conditions required for activation of BK channels in Purkinje neurons, the dependence of BK channel open probability on calcium concentration and membrane voltage were investigated in excised patches from soma of acutely prepared Purkinje cells. Single channel currents were studied under conditions designed to select for potassium currents and in which voltage-activated currents were largely inactivated. Micromolar calcium concentrations activated channels with a mean single channel conductance of 266 pS. BK channels were activated by both calcium and membrane depolarization, and showed no sign of inactivation. At a given calcium concentration, depolarization over a 60-mV range increased the mean open probability (P(O)) from < 0.1 to > 0.8. Increasing the calcium concentration shifted the voltage required for half maximal activation to more hyperpolarized potentials. The apparent affinity of the channels for calcium increased with depolarization. At -60 mV the apparent affinity was approximately 35 micro m decreasing to approximately 3 micro M at +40 mV. These results suggest that BK channels are unlikely to be activated at resting membrane potentials and calcium concentrations. We tested the hypothesis that Purkinje cell BK channels may be activated by calcium entry during individual action potentials. Significant BK channel activation could be detected when brief action potential-like depolarizations were applied to patches under conditions in which the sole source of calcium was flux across the plasma membrane via the endogenous voltage-gated calcium channels. It is proposed that BK channels regulate the excitability of Purkinje cells by contributing to afterhyperpolarizations and perhaps by shaping individual action potentials.     

Intracellular activity of superior laryngeal nerve motoneurons during fictive swallowing in decerebrate rats

We examined the swallowing-related intracellular activity of motoneurons of the superior laryngeal nerve (SLN) in decerebrate, paralyzed and artificially-ventilated rats, to elucidate the neuronal mechanism of the pharyngo-esophageal and laryngo-esophageal coordination during swallowing. The majority of the SLN motoneurons exhibited respiratory rhythm (n=16; 13 inspiratory, one expiratory and two non-respiratory neurons). During fictive swallowing evoked by electrical stimulation of the SLN, all these motoneurons showed a hyperpolarization-depolarization sequence in their membrane potentials. The hyperpolarization, which was shown to consist of inhibitory postsynaptic potentials, started at the onset of the hypoglossal swallowing burst, lasted during the burst, and was followed by a depolarization at the end of the burst. This hyperpolarization-depolarization pattern implies that the SLN motoneurons may be involved in the 'inhibitory chain' within the swallowing pattern generator, which may be cardinal in the sequential activation of different populations of motoneurons innervating the swallowing-related muscles.     

Coordination of the Activity of Monoaminergic Pedal Neurons in Freshwater Snails

In the freshwater pulmonate pond snail and flateye snail, contact of the pneumostoma (the respiratory organ) with the water surface and tactile stimulation of the mantle induced phase-coordinated excitation and inhibition of activation of symmetrical pedal neurons RPeD1 (the GDC – giant dopamine cell) and LPeD1 (the GSC – giant serotonin cell). GDC and GSC are not primary sensory neurons and the mechanism by which their actions are coordinated is polysynaptic. Injections of depolarizing current into the GDC or GSC induced spike discharges in one of the columellar nerves. It is suggested that coordination the activities of the GDC and GSC is functionally important for controlling the right and left halves of the columellar complex of muscles during respiration.     

Origins and violations of the 2/3 power law in rhythmic three-dimensional arm movements

The 2/3 power law, the nonlinear relationship between tangential velocity and radius of curvature of the end-effector trajectory, is thought to be a fundamental constraint of the central nervous system in the formation of rhythmic endpoint trajectories. However, studies on the 2/3 power law have been confined largely to planar drawing patterns of relatively small size. With the hypothesis that this strategy overlooks nonlinear effects that are constitutive in movement generation, the present experiments tested the validity of the power law in elliptical patterns that were not confined to a planar surface and which were performed by the unconstrained 7-degrees of freedom (DOF) arm, with significant variations in pattern size and workspace orientation. Data were recorded from five human subjects where the seven joint angles and the endpoint trajectories were analyzed. Additionally, an anthropomorphic 7-DOF robot arm served as a "control subject" whose endpoint trajectories were generated on the basis of the human joint angle data, modeled as simple harmonic oscillations. Analyses of the endpoint trajectories demonstrate that the power law is systematically violated with increasing pattern size, in both exponent and the goodness of fit. The origins of these violations can be explained analytically based on smooth, rhythmic trajectory formation and the kinematic structure of the human arm. We conclude that, in unconstrained rhythmic movements, the power law seems to be a by-product of a movement system that favors smooth trajectories, and that it is unlikely to serve as a primary movement-generating principle. Our data rather suggest that subjects employed smooth oscillatory pattern generators in joint space to realize the required movement patterns.     

Perception of angular head position during attempted alignment with eccentric visual objects

The perception of angular head position with respect to a visual object was investigated using three different methods: Pointer indication (P); in the dark, subjects' (Ss') heads were horizontally turned to various positions (range +/- 54 degrees); Ss then rotated a pointer carrying a light emitting diode (LED) so as to align it with head position. Active head pointing (A); again in darkness, the pointer was rotated to various positions; Ss then turned their heads so as to align them with the pointer. Reading from visible scale (V); Ss viewed a degrees scale on a circular screen; Ss' heads were turned as in P, and Ss reported head position in terms of this scale. The results obtained with all three methods indicate that head position is overestimated with respect to the visual object (LED, scale mark): object position exceeded head position by 6, 18, and 7% when measured with the P-, A-, and V-methods, respectively (median values). The observed misalignment between head and object suggests that subjective primary eye position is shifted in the direction of head rotation by a cross-talk of head position. Whether a functional advantage or merely a tolerated side-effect of other constraints, this behavior confers the impression of looking "straight ahead" in the literal sense when gaze is shifted by coordinated eye-head movements with a 10% eye and a 90% head share in total lateral displacement. In an attempt to probe a hypothesized internal representation of head position implied in head-to-object alignment, Ss were also to estimate head position in space using only neck proprioceptive information. In complete darkness, responses were often non-linear functions of head position with overestimation of large eccentricities. When a head-centered LED was added (which conveyed no position information), responses became more linear, suggesting that the mere presence of visual afferents may improve the perceptual interpretation of proprioceptive information.     

Neuronal coordination of arm and leg movements during human locomotion

We aimed to study the neuronal coordination of lower and upper limb muscles. We therefore evaluated the effect of small leg displacements during gait on leg and arm muscle electromyographic (EMG) activity in walking humans. During walking on a split-belt treadmill (velocity 3.5 km/h), short accelerations or decelerations were randomly applied to the right belt during the mid or end stance phase. Alternatively, trains of electrical stimuli were delivered to the right distal tibial nerve. The EMG activity of the tibialis anterior (TA), gastrocnemius medialis (GM), deltoideus (Delt), triceps (Tric) and biceps brachii (Bic) of both sides was analysed. For comparison, impulses were also applied during standing and sitting. The displacements were followed by specific patterns of right leg and bilateral arm muscle EMG responses. Most arm muscle responses appeared with a short latency (65-80 ms) and were larger in Delt and Tric than in Bic. They were strongest when deceleration impulses were released during mid stance, associated with a right compensatory TA response. A similar response pattern in arm muscles was obtained following tibial nerve stimulation. The arm muscle responses were small or absent when stimuli were applied during standing or sitting. The arm muscle responses correlated more closely with the compensatory TA than with the compensatory GM responses. The amplitude of the responses in most arm muscles correlated closely with the background EMG activity of the respective arm muscle. The observations suggest the existence of a task-dependent, flexible neuronal coupling between lower and upper limb muscles. The stronger impact of leg flexors in this interlimb coordination indicates that the neuronal control of leg flexor and extensor muscles is differentially interconnected during locomotion. The results are compatible with the assumption that the proximal arm muscle responses are associated with the swinging of the arms during gait, as a residual function of quadrupedal locomotion.