PROCEEDINGS OF THE PHYSIOLOGICAL SOCIETY DUNDEE MEETING
28-29 June 1991 These abstracts were accepted by Members of the Society present at the Meeting
J. Physiol. (1992) Vol. 446. Dundee Meeting 28-29 June 1991
PROCEEDINGS OF THE PHYSIOLOGICAL SOCIETY
2P
DEMONSTRATIONS Use of a biasing torque, high inertia mechanical filter, and automatic readout system for human ankle jerk measurements E.G. Walsh and G.W. Wright Department of Physiology, University of Edinburgh, Edinburgh EH8 9AG Timing of the events following a tendon tap offers the opportunity of rapidly and non-invasively obtaining some information about muscle properties and
has been used to monitor thyroid function (Lambert et al. 1951). According to one report the mechanical response is much shorter in spastic children (Wall et al. 1964). The isotonic system used was however not wholly satisfactory as the swing will have been influenced by the weight of the foot, the position of the centre of gravity, the inertia about the ankle and the passive elasticity of the dorsiflexors. These extraneous factors are essentially eliminated using an isometric technique. It is however tiresome if the initial load on the transducer depends on the weight of the foot and the degree of relaxation for repeated electrical rebalancing may be necessary. We have argued that it would be better to start with the ankle subjected to a defined constant dorsiflexing torque whilst the ensuing contraction is recorded isometrically. The patient lies on his side with the sole of the foot applied to a 100 kg (RS) load cell. The cell is mounted on a horizontal beam, 1 m long, supported at its centre by the spindle of a large printed motor (G19M4). The motor, energised with an adjustable current of up to several amps, applies a controllable dorsiflexing force. At the ends of the beam are fixed weights of 10 kg each. Because of this high inertia the contraction is almost over before there is appreciable movement which, in any event, is quite small. An electronic system displays digitally the peak force, half-contraction time and the half-relaxation time. To obtain the half-contraction time a delay line is used. The circuits are reset at each trial by a switch in the tendon hammer. It is thus possible to obtain the measurements of a number of trials quickly. Supported by the James and Grace Anderson Trust. REFERENCES
Lambert, E.H., Underdahl, L.O., Beckett, S. & Mederos, L.O.(1951). J. Clin. Endocrin. 11, 11861205.
Wall, R.L., Umlauf, H.J. & Geppert, L.J.(1964). J. Pediat. 64, 701-710.
J. Physiol. (1992) Vol. 446. Proceedings of The Physiological Society
DUNDEE MEETING 28-29 JUNE 1991
3P
Digital colour image display and capture for computer-assisted on the Apple Macintosh computer
learning programmes
J.F. Aiton, C.G. Ingram and J.J. O'Connor* Department of Biology & Pre-clinical Medicine and *Department of Mathematics & Computational Sciences, University of St Andrews, St Andrews, Fife KY16 9TS
Although interactive laser video disk technology has an important role to play in computer-based education and training, much of the visual information for simple teaching programmes appears as single frames (slides, diagrams, still photographs etc). The cost of production and display of video disk images, coupled with the frequent inability of a staff members to find the image they require, has led us to evaluate other hardware/software alternatives capable of providing high quality colour images on computers which are suitable for student use. The recent development of digital video adapters for personal computers has made it possible to display and capture live video colour images from a number of different video input sources on standard computer monitors. The frames can then be stored as digital image files for incorporation into computer assisted learning programmes (Hanka et al. 1991). The video image capture system we employ uses an Apple Macintosh Ilci fitted with a VideoLogic DVA-4000 full motion digital video adapter (VideoLogic Limited, Kings Langley, Herts) which can display and manipulate high quality live video images on a standard Macintosh 13" colour monitor. The DVA-4000 board accepts input from a number of different analogue sources such as video disk, video tape, off-air TV, still video cameras and camcorders in a number of different video input formats including composite (PAL or NTSC), RGB and S-Video. In addition to allowing sophisticated video and graphics integration, the software which accompanies the DVA-4000 board permits precise image capture. Any incoming video image source can be browsed, dynamically resized and frozen in the display window. Standard Macintosh screen area selection techniques allow specific areas of the image to be captured in 24 bit true colour PICT format and saved to disk as an image file. Thus far we have captured images from an S-VHS camcorder, a laser disk player, video cameras mounted on both compound and dissection microscopes and a Tamron Fotovix 35mm slide display system. If necessary, the colour balance of the 24 bit colour images (a colour palette of up to 16.7 million hues) can be modified with image processing software (e.g. Adobe Photoshop) and converted to 16 bit colour (a colour palette of approximately 32,000 hues) for display on the student workstations. These workstations are Apple Macintosh LC computers fitted with an additional 512K of VRAM (video RAM) to display the 16 bit images on Apple 12" colour monitors (512x384 pixel resolution). Our teaching programmes are being developed with HyperCard 2.0 which can display colour images (up to 24 bit) by calling custom XCMDs (external commands) from HyperTalk, the HyperCard programming language. We are grateful to Dr Ian Low for his financial support in setting up this project. REFERENCE Hanka, R., Stephens, C. & Thompson, P. (1991). The CTISS File 11, 10-14.
J. Physiol. (1992) Vol. 446. Dundee Meeting 28-29 June 1991
iP
PROCEEDINGS OF THE PHYSIOLOGICAL SOCIETY
Does a ptretch reflex contribute to the excitations which follow inhibitory jaw reflexes in man? Stella Mitchell, C.H. Lloyd* and S.W. Cadden Departments of Dental Surgery (Oral Biology) and *Dental Prosthetics & Gerontology, The Dental School, University of Dundee, Dundee DD1 4HN
The most prominent reflexes produced by stimulation of oro-facial structures in man are those which involve inhibitions of activity in jaw closing muscles such as the masseter. However, these inhibitory reflexes are almost always followed by periods during which activity in the muscle is increased. Amongst several explanations which have been proposed for these post-inhibitory excitations is that they are due to a stretch reflex resulting from the relaxation and stretch of the masseter during the inhibitory period (e.g. Yemm, 1972). The purpose of the present experiments is to investigate this possibility. Experiments are performed on volunteer subjects who have given informed consent. In outline, the experiments involve recording responses in the active masseter muscle to electrical stimulation of the lip while the subjects bite on spring devices of differing stiffnesses. The hypothesis being tested is that, if stretch reflexes do contribute to the post-inhibitory excitations, then the less stiff the spring the greater should be the excitation which follows a given degree of inhibition; the logic being that the less stiff the spring, the more it will be compressed at a given level of masseteric activity, the more it will recoil and hence stretch the muscle during the inhibition and therefore the greater will be the stretch reflex. The spring devices consist of small acrylic trays attached to stainless steel beams which are attached at their other ends to a small block of steel. By varying the length of the beams, the stiffness of the device can be altered. The acrylic trays contain hard impressions of the upper and lower posterior teeth of the subject and thus allow the devices to be located in the same position every time. The EMG recordings are made via skin surface electrodes placed over the masseter and the stimuli are applied via similar electrodes on the upper lip. The stimuli consist of Ims constant-current pulses at intensities of 1, ?, 5, 10 and 20 times perception threshold. Responses to 8 such stimuli, applied 1/4 s, are full-wave-rectified, averaged and smoothed and the magnitudes of the inhibitory response and subsequent excitations are determined by integration. Throughout each sequence, the subjects are given visual feedback of their rectified, filtered (DC-5Hz) EMG and asked to maintain the level at 10% of the maximum which they can produce. Regression analyses are performed on the excitations against inhibitions for each of 4 stiffnesses of spring (6.5, 13 and 27 N/mm and one of near infinite stiffness). The resulting regression lines are compared by establishing 95% confidence limits. REFERENCE
Yemm, R. (1972). Arch. Oral Biol. 17, 23-33.
J. Physiol. (1992) Vol. 446. Proceedings of The Physiological Society
DUNDEE MEETING 28-29 JUNE 1991
5P
Computer-based reconstruction of the innervation to the maxillary teeth and air sinus (lateral nasal recess) in the ferret A.G. Mason and G.S. McKay Department of Dental Surgery (Oral Biology), The Dental School, The University of Dundee, Dundee DD1 4HN
A means of standardizing the application of electrical stimuli to intra-oral structures during studies of jaw reflexes in man J.P. Newton, K.C. Sturrock, A.M. Munro and S.W. Cadden* Departments of Dental Prosthetics & Gerontology and *Dental Surgery (Oral Biology), The Dental School, University of Dundee, Dundee DD1 4HN
28-29 June 1991 These abstracts were accepted by Members of the Society present at the Meeting
J. Physiol. (1992) Vol. 446. Dundee Meeting 28-29 June 1991
PROCEEDINGS OF THE PHYSIOLOGICAL SOCIETY
2P
DEMONSTRATIONS Use of a biasing torque, high inertia mechanical filter, and automatic readout system for human ankle jerk measurements E.G. Walsh and G.W. Wright Department of Physiology, University of Edinburgh, Edinburgh EH8 9AG Timing of the events following a tendon tap offers the opportunity of rapidly and non-invasively obtaining some information about muscle properties and
has been used to monitor thyroid function (Lambert et al. 1951). According to one report the mechanical response is much shorter in spastic children (Wall et al. 1964). The isotonic system used was however not wholly satisfactory as the swing will have been influenced by the weight of the foot, the position of the centre of gravity, the inertia about the ankle and the passive elasticity of the dorsiflexors. These extraneous factors are essentially eliminated using an isometric technique. It is however tiresome if the initial load on the transducer depends on the weight of the foot and the degree of relaxation for repeated electrical rebalancing may be necessary. We have argued that it would be better to start with the ankle subjected to a defined constant dorsiflexing torque whilst the ensuing contraction is recorded isometrically. The patient lies on his side with the sole of the foot applied to a 100 kg (RS) load cell. The cell is mounted on a horizontal beam, 1 m long, supported at its centre by the spindle of a large printed motor (G19M4). The motor, energised with an adjustable current of up to several amps, applies a controllable dorsiflexing force. At the ends of the beam are fixed weights of 10 kg each. Because of this high inertia the contraction is almost over before there is appreciable movement which, in any event, is quite small. An electronic system displays digitally the peak force, half-contraction time and the half-relaxation time. To obtain the half-contraction time a delay line is used. The circuits are reset at each trial by a switch in the tendon hammer. It is thus possible to obtain the measurements of a number of trials quickly. Supported by the James and Grace Anderson Trust. REFERENCES
Lambert, E.H., Underdahl, L.O., Beckett, S. & Mederos, L.O.(1951). J. Clin. Endocrin. 11, 11861205.
Wall, R.L., Umlauf, H.J. & Geppert, L.J.(1964). J. Pediat. 64, 701-710.
J. Physiol. (1992) Vol. 446. Proceedings of The Physiological Society
DUNDEE MEETING 28-29 JUNE 1991
3P
Digital colour image display and capture for computer-assisted on the Apple Macintosh computer
learning programmes
J.F. Aiton, C.G. Ingram and J.J. O'Connor* Department of Biology & Pre-clinical Medicine and *Department of Mathematics & Computational Sciences, University of St Andrews, St Andrews, Fife KY16 9TS
Although interactive laser video disk technology has an important role to play in computer-based education and training, much of the visual information for simple teaching programmes appears as single frames (slides, diagrams, still photographs etc). The cost of production and display of video disk images, coupled with the frequent inability of a staff members to find the image they require, has led us to evaluate other hardware/software alternatives capable of providing high quality colour images on computers which are suitable for student use. The recent development of digital video adapters for personal computers has made it possible to display and capture live video colour images from a number of different video input sources on standard computer monitors. The frames can then be stored as digital image files for incorporation into computer assisted learning programmes (Hanka et al. 1991). The video image capture system we employ uses an Apple Macintosh Ilci fitted with a VideoLogic DVA-4000 full motion digital video adapter (VideoLogic Limited, Kings Langley, Herts) which can display and manipulate high quality live video images on a standard Macintosh 13" colour monitor. The DVA-4000 board accepts input from a number of different analogue sources such as video disk, video tape, off-air TV, still video cameras and camcorders in a number of different video input formats including composite (PAL or NTSC), RGB and S-Video. In addition to allowing sophisticated video and graphics integration, the software which accompanies the DVA-4000 board permits precise image capture. Any incoming video image source can be browsed, dynamically resized and frozen in the display window. Standard Macintosh screen area selection techniques allow specific areas of the image to be captured in 24 bit true colour PICT format and saved to disk as an image file. Thus far we have captured images from an S-VHS camcorder, a laser disk player, video cameras mounted on both compound and dissection microscopes and a Tamron Fotovix 35mm slide display system. If necessary, the colour balance of the 24 bit colour images (a colour palette of up to 16.7 million hues) can be modified with image processing software (e.g. Adobe Photoshop) and converted to 16 bit colour (a colour palette of approximately 32,000 hues) for display on the student workstations. These workstations are Apple Macintosh LC computers fitted with an additional 512K of VRAM (video RAM) to display the 16 bit images on Apple 12" colour monitors (512x384 pixel resolution). Our teaching programmes are being developed with HyperCard 2.0 which can display colour images (up to 24 bit) by calling custom XCMDs (external commands) from HyperTalk, the HyperCard programming language. We are grateful to Dr Ian Low for his financial support in setting up this project. REFERENCE Hanka, R., Stephens, C. & Thompson, P. (1991). The CTISS File 11, 10-14.
J. Physiol. (1992) Vol. 446. Dundee Meeting 28-29 June 1991
iP
PROCEEDINGS OF THE PHYSIOLOGICAL SOCIETY
Does a ptretch reflex contribute to the excitations which follow inhibitory jaw reflexes in man? Stella Mitchell, C.H. Lloyd* and S.W. Cadden Departments of Dental Surgery (Oral Biology) and *Dental Prosthetics & Gerontology, The Dental School, University of Dundee, Dundee DD1 4HN
The most prominent reflexes produced by stimulation of oro-facial structures in man are those which involve inhibitions of activity in jaw closing muscles such as the masseter. However, these inhibitory reflexes are almost always followed by periods during which activity in the muscle is increased. Amongst several explanations which have been proposed for these post-inhibitory excitations is that they are due to a stretch reflex resulting from the relaxation and stretch of the masseter during the inhibitory period (e.g. Yemm, 1972). The purpose of the present experiments is to investigate this possibility. Experiments are performed on volunteer subjects who have given informed consent. In outline, the experiments involve recording responses in the active masseter muscle to electrical stimulation of the lip while the subjects bite on spring devices of differing stiffnesses. The hypothesis being tested is that, if stretch reflexes do contribute to the post-inhibitory excitations, then the less stiff the spring the greater should be the excitation which follows a given degree of inhibition; the logic being that the less stiff the spring, the more it will be compressed at a given level of masseteric activity, the more it will recoil and hence stretch the muscle during the inhibition and therefore the greater will be the stretch reflex. The spring devices consist of small acrylic trays attached to stainless steel beams which are attached at their other ends to a small block of steel. By varying the length of the beams, the stiffness of the device can be altered. The acrylic trays contain hard impressions of the upper and lower posterior teeth of the subject and thus allow the devices to be located in the same position every time. The EMG recordings are made via skin surface electrodes placed over the masseter and the stimuli are applied via similar electrodes on the upper lip. The stimuli consist of Ims constant-current pulses at intensities of 1, ?, 5, 10 and 20 times perception threshold. Responses to 8 such stimuli, applied 1/4 s, are full-wave-rectified, averaged and smoothed and the magnitudes of the inhibitory response and subsequent excitations are determined by integration. Throughout each sequence, the subjects are given visual feedback of their rectified, filtered (DC-5Hz) EMG and asked to maintain the level at 10% of the maximum which they can produce. Regression analyses are performed on the excitations against inhibitions for each of 4 stiffnesses of spring (6.5, 13 and 27 N/mm and one of near infinite stiffness). The resulting regression lines are compared by establishing 95% confidence limits. REFERENCE
Yemm, R. (1972). Arch. Oral Biol. 17, 23-33.
J. Physiol. (1992) Vol. 446. Proceedings of The Physiological Society
DUNDEE MEETING 28-29 JUNE 1991
5P
Computer-based reconstruction of the innervation to the maxillary teeth and air sinus (lateral nasal recess) in the ferret A.G. Mason and G.S. McKay Department of Dental Surgery (Oral Biology), The Dental School, The University of Dundee, Dundee DD1 4HN
A means of standardizing the application of electrical stimuli to intra-oral structures during studies of jaw reflexes in man J.P. Newton, K.C. Sturrock, A.M. Munro and S.W. Cadden* Departments of Dental Prosthetics & Gerontology and *Dental Surgery (Oral Biology), The Dental School, University of Dundee, Dundee DD1 4HN
