Mechanical sensibility of the sole of the foot determined with vibratory stimuli of varying frequency

Summary The mechanoreceptive properties of the sole of the foot were determined by measuring the detection thresholds to vibratory stimuli of 20, 80, and 240 Hz frequency and 300 ms duration. The thresholds were measured at six different sites on the left sole and at toes 1 and 3 with probes of 2 and 8 mm diameter connected to the moving coil of an electromechanical vibrator. The subject sat in an armchair during the experiments, with the left leg supported horizontally by a vacuum cast positioned on a table. Six subjects participated in the experiments. A simple method of limits was used to make the measurements. Lower average thresholds were obtained with higher vibration frequencies, the average thresholds varying between 40–90 m at 20 Hz and well below 10 m at 240 Hz. The major decrease in thresholds occurred between 20 and 80 Hz. Interindividual variability in thresholds was large, but the threshold curves obtained from different subjects and from different stimulation points were of the same general shape. The highest thresholds were measured from the toes, but this regional difference in sensibility was obtained only at the higher vibration frequencies. Comparison of the threshold values at the sole with those found with similar stimuli at the thenar eminence and middle fingertip indicates that the mechanoreceptor mechanisms transmitting information about low-frequency vibration in the sole are similar to those in the palmar skin of the hand.     

Response of rapidly and slowly adapting mechanoreceptors and vibratory sensitivity in human hairy skin

Summary Single unit activity was recorded percutaneously with microelectrodes from 38 rapidly adapting (RA) mechanoreceptors of the dorsal surface of the hand in 49 awake human subjects. Tuning characteristics were determined for 28 RA-fibers at various frequencies between 5 and 100 cps of sinusoidal mechanical stimulation. In separate experiments human thresholds of vibration perception were studied under comparable conditions.Several RA-mechanoreceptive fibers were broadly tuned, showing no clearly defined best frequency in the range between 5 and 20 cps. Other RA-fibers had a minimum of sensitivity between 20 and 40 cps. For either lower or higher frequencies, stronger stimuli were required to elicit one nerve impulse per stimulus cycle. These RA-receptors may be related to the perception of low frequency oscillation (flutter). They cannot account for human vibration sensitivity in the higher frequency range, since tuning of the receptors required considerably higher amplitudes than perception.Sixteen slowly adapting (SA) mechanoreceptors of Type I and II showed a frequency modulation in phase with low frequency mechanical oscillations of stimulus amplitudes far below human thresholds for perception of movement.Supported by the Deutsche ForschungsgemeinschaftA preliminary account of a part of these results was presented at the 47th Meeting of the German Physiological Society, Regensburg, 1976 (Konietzny and Hensel, 1976)     

Relation between brain and body growth in allied rats.

Cranial volumes were measured from museum specimens of wild-caught and laboratory-born Allied rats from eastern Australia. The relation of these volumes to body weight and body length, and also to age at death in the laboratory-reared sample, was determined. Growth of both brain and body was rapid during the first three postnatal months and slowed markedly over the next month, but appeared to continue at a very slow rate throughout life. In particular, the major surge in brain growth occurred in the first three postnatal weeks. Modified Gompertzian growth functions describe the pattern of growth quite well, though the nature of the data precluded highly sensitive fits. Three features were clear: 1) the rate of slowing of growth was about the same for all variables, 2) growth appeared to continue throughout the life of the animal, and 3) the trajectory of brain growth led that of body growth by about four days. The pattern of growth in Allied rats is similar to that of laboratory rats and probably to those in other murids.     

Relation between estrogen-induced hyperlipemia and food intake and body weight in rats

Thirteen experiments on 348 ovariectomized female rats examined the relationship between estradiol's effects on food intake and body weight and on plasma triglycerides, free glycerol, and fatty acids. The time course of estradiol benzoate effects on food intake and weight gain differed from the time course of triglyceride elevation. The antiestrogen, nafoxidine, given with estradiol blocked the hypertriglyceridemia, but not the weight loss, resulting from estradiol benzoate. Estradiol benzoate treatment for up to three days had no significant effect on plasma triglyceride levels following intragastric and intravenous triglyceride administration. Changes in plasma triglyceride following Triton WR-1339 indicated that the absolute rates of plasma triglyceride clearance were not impaired by estradiol. These results contradict Wade and Gray's [31] hypothesis about the mechanism of estradiol-induced hypophagia.     

Relation between body mass index and depression: a structural equation modeling approach

Background  

Obesity and depression are two major diseases which are associated with many other health problems such as hypertension, dyslipidemia, diabetes mellitus, coronary heart disease, stroke, myocardial infarction, heart failure in patients with systolic hypertension, low bone mineral density and increased mortality. Both diseases share common health complications but there are inconsistent findings concerning the relationship between obesity and depression. In this work we used the structural equation modeling (SEM) technique to examine the relation between body mass index (BMI), as a proxy for obesity, and depression using the Canadian Community Health Survey, Cycle 1.2.     

Effects of vibration on arm and shoulder muscles in three body postures

Summary The electromyographic responses of arm and shoulder muscles to vibrations were studied in three postures similar to the postures of drilling in a ceiling, drilling in a wall and drilling in a floor. This experiment was performed within the defined parameters of: vibrational frequency at 30 Hz, acceleration level 40 m·s⁻² (rms), pushing force expressed as percentage maximal voluntary contraction, and gripping force which was set at 100 N. The exposure time for each test was 5 min. The general findings from these three body postures show that all the examined muscles were affected by exposure to vibration. The EMG index increased as follows: trapezius muscle 39% (p<0.05), lower-arm flexor muscles 23% (p<0.05), infraspinatus muscle 14% (p<0.05), lower-arm extensor muscles 14% (p<0.1) and biceps muscle 6% (p<0.1). The muscle most affected by vibration was found to be the trapezius muscle. It should be taken into consideration that vibration can be a contributing factor in neck/shoulder disorders among power handtool operators. The general conclusion from this study is that changes in working posture give different transmissions of vibration in the upper extremities. It seems as if the prime movers and muscles with an increased muscle length or increased degree of contraction are most affected by vibration.     

Relation between muscle response onset and body segmental movements during postural perturbations in humans

Summary This study has examined the individual movements of the body segments of a group of 10 standing adults during anterior and posterior platform displacements (3 and 6 cm amplitudes), and compared body movements to neck and ankle muscle response onset times. Differences in the kinematics of movement were observed for anterior vs. posterior platform displacements: hip, shoulder, and head began to move much earlier for posterior compared to anterior platform movements. This could explain differences in postural muscle temporal response organization for the two directions of body movement. Though anterior/posterior neck and head displacements were late in comparison to neck flexor muscle response onset, small vertical movements of the shoulder and head occurred early (40 and 67 ms after platform movement onset). These movements were consistently directed upward for anterior platform displacements and downward for posterior platform displacements. In order to determine whether neck proprioceptors were responsible for response activation in the neck we repeated the experiment using a neck stabilization device, on one of our subjects. In this condition, we found normal neck muscle response latencies. This suggests that neck proprioceptors are not the primary contributors to the early neck muscle responses seen during horizontal support surface displacements. In studying the effect of repeated exposure to horizontal platform displacements we found a diminution in the amplitude and an increase in onset latencies in neck and antagonist ankle muscle responses over the sequence of 16 trials, in many of the subjects tested. This corresponded to smaller head accelerations, and smaller displacements of the head and shoulder in later trials in the experimental sequence. The result implies that these subjects changed their postural set during the course of the experiment, possibly by relaxing the muscles of the body to allow the viscoelastic properties of the lower body segments to absorb more of the impact of platform displacement.     

Effects of body orientation, load and vibration on sensing position and movement at the human elbow joint

Experiments were carried out to study the ability of human subjects to match the position of their forearms relative to the horizontal. The normal, arms-in-front position with the hands aligned and little forward flexion at the shoulder was called the reference position. When the arms were rotated to the side, one arm was raised, or both arms were raised, matching ability deteriorated compared with the reference position, when expressed as an increase in the standard deviation of matching errors. It was concluded that particular significance was assigned by the brain to the arms-in-front position, with the hands in their normal working space. Increases in errors were also observed when the reference arm was made weightless or its weight was increased by means of an adjustable load. This suggested that lifting the arm against gravity provided additional positional information. In a second experiment, dependence of the illusion of muscle lengthening evoked by vibration was tested after two different forms of muscle conditioning, a co-contraction of elbow muscles with the arm held flexed or with it held extended. The speed of the illusory extension of flexor muscles during their vibration increased three-fold after flexion conditioning compared with extension conditioning. Since after flexion conditioning, muscle spindles in flexor muscles are expected to be more sensitive to vibration than after extension conditioning, this observation provides additional support for the view that muscle spindles make an important contribution to kinaesthesia at the elbow joint.     

Relation between acute phase proteins and body defense: application to the monitoring of infectious states

All acute and/or chronic pathological processes resulting in tissue damage and destruction lead to an inflammatory response. The purpose of this response is homeostatic and is made up of local and systemic events, the signs of which, taken as a whole, constitute the acute phase syndrome. Among the metabolic changes occurring in this syndrome, the rise in the plasma concentration of a group of heterogenous proteins known as the "Acute Phase Reactant Proteins" ( APRP ) is a very reliable and sensitive indicator of the presence of pathology. Most of these proteins are involved in the mechanisms initiating and controlling the inflammatory response. Some of them seem to establish a link between the body's specific and non-specific defence mechanisms. APRP are indicators of the inflammatory response without being specific to a particular etiology. The degree of variation in APRP levels is not generally speaking a good indicator of the severity or spread of the tissue lesions. On the other hand, they are very useful for detecting and monitoring infectious and/or inflammatory states, whether these are being treated or not. Thus during anti-infectious or anti-inflammatory treatment the return of APRP levels to their physiological baseline is a very good argument in favour of the efficacy of such treatment.     

护理专业体表标志教学探讨

为社会输送护理技能型人才是中等护理专业的主要培养目标，护理操作技能训练是护理专业教育中极为重要。人体解剖学是护理专业重要的医学基础课，如何结合培养目标加强解剖学基本技能教学，为护理学操作技能的学习打下扎实的基础，是值得解剖学教师重视的问题。本文在护理专业运动系统教学中，对活体体表标志教学进行初步探讨。     

Time correlation between initial activation of ventricular myocardium and cardiac electric potentials on body surface in dogs

Parameters of cardioelectric field on body surface and propagation of excitation in ventricular myocardium during initial activation were studied using multichannel synchronous electrocardiotopography. It was shown that inversion of areas of negative and positive potentials of cardioelectric field on body surface at the moment of excitation propagation to the epicardium reflected changes in the main direction of excitation wavefront in ventricles.     

Dependence of biomechanical impedance upon living body structure

A physical model for biomechanical impedance has already been proposed. This model is characterised by three impedance spectra: soft, intermediate and hard pattern. An impedance spectrum of the body surface represents mostly the soft pattern, The formative mechanisms of all three patterns have been unsolved until now. Because the physical model is expressed by experimental equations, its theoretical background is not apparent. In the paper a simulating material (simulator) is used, whose tactility is not unlike human skin, and the formative mechanism of biomechanical impedance is revealed through experiments on the simulator under various measuring conditions. The influences of the measuring circumstances, living body structure and physical constants of the body tissues on the experimental equations of the physical model are fully discussed. The formative mechanism of biomechanical impedance which represents the physical model is explained in terms of an equivalent mass, a dynamic equivalent stiffness, a dynamic viscosity and a composite characteristic. The dependence between body parts from which the measurements are taken and soft, intermediate and hard patterns are demonstrated.