PROCEEDINGS OF lip palette

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					      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
2P               PROCEEDINGS OF THE PHYSIOLOGICAL SOCIETY
                                   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, 1186-
  1205.
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          learning programmes
on the Apple Macintosh computer
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 moni-
tors. 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

				
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