Ron Balnave - Academia.edu (original) (raw)
Papers by Ron Balnave
The Journal of Physiology, 1977
1. End-plate potentials produced by brief trains of action potentials (5-7 at 50-100 Hz) were rec... more 1. End-plate potentials produced by brief trains of action potentials (5-7 at 50-100 Hz) were recorded at toad sciatic-sartorius neuromuscular junctions. When transmitter secretion was depressed in solutions containing magnesium, the increase in amplitude (growth pattern) of successive end-plate potentials was greater than could be accounted for by arithmetic summation of facilitation (arithmetic model) as proposed by Mallart & Martin (1967). 3. With e.p.p.s of normal quantal content or in solutions in which the calcium concentration was lowered, growth patterns were occasionally reasonably close to those predicted by the arithmetic model but there was always some degree of disparity. 4. A simple, two-step, kinetic model is described which is more consistent with the varied growth patterns of end-plate potentials that have been recorded. The model can predict growth patterns of e.p.p.s with high or with low quantal content.
British Journal of Pharmacology, 1973
1. Manganese, at low concentrations (05-20 mM), blocks neuromuscular transmission in toads. Endpl... more 1. Manganese, at low concentrations (05-20 mM), blocks neuromuscular transmission in toads. Endplate potentials (e.p.ps) are reduced in amplitude but the amplitude of miniature endplate potentials (m.e.p.ps) is, if anything, increased. 2. The release of transmitter by an action potential is reduced in solutions containing Mn, but is still well described by the Poisson equation. 3. Log-log plots of e.p.p. quantal content (m) against [Ca] have a mean gradient of 3 73, and a model based on the cooperative action of four calcium ions in excitation-secretion coupling, and competitive inhibition by Mn, was constructed. The model, with its exponent of 4, is shown in fact to predict gradients of less than four for log-log plots of m against [Ca]. 4. The assumption of competitive inhibition by Mn was supported by modified Lineweaver-Burk plots of magainst 1 /[Ca]. The mean dissociation constants for Ca and Mn were 1-3 mm and 0-15 mm respectively. From the model, an upper estimate of the density of calcium ' receptor sites ' of 30 per square micron of nerve terminal was obtained. 5. In contrast to its inhibitory effect on evoked release, Mn increases the spontaneous release of transmitter. It is suggested that Mn may increase m.e.p.p. frequency by releasing Ca from an intracellular store.
Respiration Physiology, 2000
Periaqueductal gray (PAG) and nucleus tractus solitarius (NTS) are important centres for regulati... more Periaqueductal gray (PAG) and nucleus tractus solitarius (NTS) are important centres for regulation of cardiorespiratory function in cats. We aimed to study the effects of specific PAG stimulation on cardiorespiratory parameters in the rat. Microinjection of D,L-homocysteic acid (DLH) into dorsolateral PAG of anaesthetised rats, led to: marked increases in respiratory frequency (RF) and amplitude of diaphragmatic electromyogram, decreases in inspiratory and expiratory durations, and increased blood pressure and heart rate. Following injection of propranolol (150 pmol, 30 nl), a beta-adrenergic antagonist, into the commissural subnucleus of NTS, the DLH-induced increase in RF was markedly attenuated. Inspiratory neurones (late I cells) in NTS were excited upon stimulation of PAG and their increased activity was accompanied by increased RF. The changes in activity of the late I cells in response to stimulation of dorsolateral PAG provide physiological evidence of a link, possibly noradrenergic, between the two nuclei and involvement of the NTS in control of respiratory functions orchestrated by the PAG.
Journal of voice : official journal of the Voice Foundation, 2021
Journal of Voice
In the cat four different types of vocalization, mews, howls, cries, and hisses were generated by... more In the cat four different types of vocalization, mews, howls, cries, and hisses were generated by microstimulation in different parts of the periaqueductal gray (PAG). While mews imply positive vocal expressions, howls, hisses, and cries represent negative vocal expressions. In the intermediate PAG, mews were generated in the lateral column, howls, and hisses in the ventrolateral column. Cries were generated in two other regions, the lateral column of the rostral PAG and the ventrolateral column of the caudal PAG. In order to define the specific motor patterns of the mews, howls, and cries, the following muscles were recorded during these vocalizations; larynx (cricothyroid, thyroarytenoid, and posterior cricoarytenoid), tongue (genioglossus), jaw (digastric), and respiration muscles (diaphragm, internal intercostal, external, and internal abdominal oblique). During these mews, howls, and cries we analyzed the frequency, intensity, activation cascades power density, turns, and amplitude analysis of the electromyograms (EMGs). It appeared that each type of vocalization consists of a specific circumscribed motor coordination. The nucleus retroambiguus (NRA) in the caudal medulla is known to serve as the final premotor interneuronal output system for vocalization. Although neurochemical microstimulation in the NRA itself also generated vocalizations, they only consisted of guttural sounds, the EMGs of which involved only small parts of the EMGs of the mews, howls, and cries generated by neurochemical stimulation in the PAG. These results demonstrate that positive and negative vocalizations are generated in different parts of the PAG. These parts have access to different groups of premotoneurons in the NRA, that, in turn, have access to different groups of motoneurons in the brainstem and spinal cord, resulting in different vocalizations. The findings would serve a valuable model for diagnostic assessment of voice disorders in humans.
Journal of Comparative Neurology
The nucleus retroambiguus (NRA) is a neuronal cell group in the medullary ventrolateral tegmentum... more The nucleus retroambiguus (NRA) is a neuronal cell group in the medullary ventrolateral tegmentum, rostrocaudally between the obex and the first cervical spinal segment. NRA neurons are premotor interneurons with direct projections to the motoneurons of soft palate, pharynx, and larynx in the nucleus ambiguus in the lateral medulla as well as to the motoneurons in the spinal cord innervating diaphragm, abdominal, and pelvic floor muscles and the lumbosacral motoneurons generating sexual posture. These NRA premotor interneurons receive very strong projections from the periaqueductal gray (PAG) in the context of basic survival mechanisms as fight, flight, freezing, sound production, and sexual behavior. In the present study in rat we investigated the physiological motor patterns generated by NRA neurons, as the result of vagal, peripheral chemosensory, and nociceptive stimulation. The results show that the NRA contains phasic respiratory modulated neurons, as well as nonphasic tonically modulated neurons. Stimulation in the various rostrocaudal levels of the NRA generates site-specific laryngeal, respiratory, abdominal, and pelvic floor motor activities. Vagal and peripheral chemosensory stimulation induces both excitatory and inhibitory modulation of phasic NRA-neurons, while peripheral chemosensory and nociceptive stimulation causes excitation and inhibition of nonphasic NRA-neurons. These results are in agreement with the concept that the NRA represents a multifunctional group of neurons involved in the output of the emotional motor system, such as vomiting, vocalization, mating, and changes in respiration.
Ergonomics, Mar 27, 2007
The use of measures of strength variability as a means of determining sincerity of effort is beco... more The use of measures of strength variability as a means of determining sincerity of effort is becoming a more common practice, particularly in medico-legal and rehabilitation settings. The stability of such variability measures, however, has not been documented. This research investigated, in two studies, the trial-to-trial variability of grip strength under maximal and submaximal effort conditions. In the first study, 63 subjects were asked to give 100% grip effort, and in the second study 40 subjects from the original group were asked to give 50% grip effort. The Jamar hand dynamometer was used to measure grip strength in both experiments, and a coefficient of variation (CV) was calculated for every three repeat measures at each handle position. Testing was conducted on two separate occasions for both experiments. Although the interoccasion reliability of grip strength was very high, in comparison, the CV was not stable over test occasions, with interoccasion reliability indices close to zero. Factors significantly influencing CV were effort level, with submaximal effort producing larger CVs, and gender, with females having greater strength variability. If the rule is applied that one or more CVs above the 7.5% cut-off value could indicate submaximal effort, then for this sample of subjects giving maximal effort, 97% of females and 64% of males would be misclassified. Applying a single CV classification cut-off value to a mixed sample of subjects appears to unfairly discriminate against the females. Further research into the factors associated with high CV values is essential before the CV can be used with any confidence in a clinical setting as a method for determining sincerity of effort.
The Journal of Physiology, 1974
1. The time dependence of the increase in amplitude (facilitation) of a second end-plate potentia... more 1. The time dependence of the increase in amplitude (facilitation) of a second end-plate potential (e.p.p.) elicited within 10-100 msec of a preceding e.p.p. was examined at neuromuscular junctions in sartorius muscles of toads. Facilitation was defined by two characteristics, initial facilitation and the time constant of its exponential decay. 2. The time constant of decay of facilitation was longer at lower temperatures and the Q10 was 4'3 in the range 10-250 C. There was no significant effect of temperature on initial facilitation. 3. Ouabain (104-10-3 M), lithium substitution for sodium, sodium azide (5 mM) and N-ethylmaleimide (NEM, 0.1 mm) initially had no effect on initial facilitation or the decay of facilitation. After some time, they all caused a longer time constant of decay of facilitation and a depression of initial facilitation. 4. It was concluded that the decay of facilitation is not directly dependent on active transport of sodium ions, calcium efflux, ATP-dependent movements of calcium or mitochondrial uptake of calcium following an action potential. 5. Ouabain, lithium, sodium azide, and NEM all caused an increase in transmitter release. This effect, and the late effects on facilitation, were thought to be due to an increase in intracellular calcium concentration in nerve terminals. 6. No relationship was found between the quantal content of e.p.p.s (range, 0.8-100) and initial facilitation, or the time constant of decay of facilitation. 7. Substitution of strontium for calcium ions caused a marked prolongation of the time constant of decay of facilitation, and a depression of initial facilitation. 8. The results were consistent with the hypothesis that the time 27 PH Y 239 RON J. BALNAVE AND PETER W. GAGE constant of decay of facilitation is related to the rate of disappearance of an ' active' complex of calcium (CaA) which, of itself, is not sufficient for transmitter release. It is suggested that an action potential produces CaA which decays with the time constant of facilitation and CaS, a short-life complex of calcium which decays with the time constant of the phasic release of transmitter. The release of transmitter is proportional to some function of [CaA] and [CaS].
Advances in experimental medicine and biology, 2004
... Page 6. 140 HHSubramanian et aL 6 TP (cmH 0 o c, 7 D "J EO . . . . . 10s DLH Figure 6. D... more ... Page 6. 140 HHSubramanian et aL 6 TP (cmH 0 o c, 7 D "J EO . . . . . 10s DLH Figure 6. DLH into the NRA. TP: Tracheal Pressure, CT: Cricothyroid EMG, D: Diaphragm EMG, EO: External Oblique. ... Journal of Neurophysiology, 72, 1337-56. 7. Li, ZY, Xia, BL, Huang, CJ, 1992. ...
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 1984
Miniature end plate currents (MEPCs) were recorded with focal extracellular electrodes from white... more Miniature end plate currents (MEPCs) were recorded with focal extracellular electrodes from white extraocular muscle fibres of a marine teleost fish,Trachurus novaezelandiae, over a temperature range of 5 °C to 27 °C.1.Teleost MEPCs rose rapidly, attaining a maximum amplitude of 250–500 µV, withTGof about 150 µs at 15 °C (Figs. 1, 2).2.Decay of MEPCs was exponential, with t=1 ms at
Respiratory Research, 2001
Brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor are required si... more Brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor are required simultaneously for survival of dopaminergic primary sensory neurons in vivo.
Respiratory Research, 2001
Brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor are required si... more Brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor are required simultaneously for survival of dopaminergic primary sensory neurons in vivo.
Advances in Experimental Medicine and Biology, 2008
Journal of Neuroscience, 2008
The midbrain periaqueductal gray (PAG) organizes basic survival behavior, which includes respirat... more The midbrain periaqueductal gray (PAG) organizes basic survival behavior, which includes respiration. How the PAG controls respiration is not known. We studied the PAG control of respiration by injecting D,L-homocysteic acid in the PAG in unanesthetized precollicularly decerebrated cats. Injections in different parts of the PAG caused different respiratory effects. Stimulation in the dorsomedial PAG induced slow and deep breathing and dyspnea. Stimulation in the dorsolateral PAG resulted in active breathing and tachypnea consistent with the respiratory changes during fright and flight. Stimulation in the medial part of lateral PAG caused inspiratory apneusis. Stimulation in lateral parts of the lateral and ventrolateral PAG produced respiratory changes associated with vocalization (mews, alternating mews and hisses, or hisses). D,L-Homocysteic acid injections in the caudal ventrolateral PAG induced irregular breathing. These results demonstrate that the PAG exerts a strong influence on respiration, suggesting that it serves as the behavioral modulator of breathing.
Safety Science, 1997
Occupational rehabilitation professionals have for many years recognised the need to develop meth... more Occupational rehabilitation professionals have for many years recognised the need to develop methods to determine whether a genuinely maximal effort is being given during clinical strength testing. A number of different sincerity of effort tests have been devised in an attempt to satisfy this need, however, in most cases the accuracy and reliability of these tests have not been adequately researched. This article reviews three of the most commonly-used sincerity of effort tests.
Respiratory Physiology & Neurobiology, 2007
The purpose of this study was to examine the effect of mechanical ventilation (MV) on inherent br... more The purpose of this study was to examine the effect of mechanical ventilation (MV) on inherent breathing and on dorsal brainstem nucleus tractus solitarius (NTS) respiratory cell function. In pentobarbitone-anaesthetised rats, application of MV at combined high frequencies and volumes (representing threshold levels) produced apnea. The apnea persisted as long as MV was maintained at or above the threshold frequency and volume. Following removal of MV, inherent breathing did not resume immediately, with the diaphragm exhibiting post-mechanical ventilation apnea. The fall in arterial P CO 2 (Pa CO 2) levels evoked by MV-engendered hyperventilation was shown not to be the trigger for initiation of apnea. MV-induced apnea was immediately reversed by bilateral vagotomy. Further, MV-induced apnea could not be evoked in bilaterally vagotomized animals suggesting that vagal feedback is the critical pathway for its initiation. NTS inspiratory neurones were inhibited during both MV-induced apnea and post-mechanical ventilation apnea, implying the involvement of central neural mechanisms in mediating this effect.
![Research paper thumbnail of Corrigendum to “Roles of periaqueductal gray and nucleus tractus solitarius in cardiorespiratory function in the rat brainstem” [Respir. Physiol. 120 (3) (2000) 185–195]](https://attachments.academia-assets.com/68021884/thumbnails/1.jpg)
](Respiratory Physiology & Neurobiology, 2013
Corrigendum Corrigendum to "Roles of periaqueductal gray and nucleus tractus solitarius in cardio... more Corrigendum Corrigendum to "Roles of periaqueductal gray and nucleus tractus solitarius in cardiorespiratory function in the rat brainstem" [Respir. Physiol. 120 (3) (2000) 185-195]
Medicine & Science in Sports & Exercise, 1994
To investigate the role of fatigue in strength training, strength increases produced by a trainin... more To investigate the role of fatigue in strength training, strength increases produced by a training protocol in which subjects rested between contractions were compared with those produced when subjects did not rest. Forty-two healthy subjects were randomly allocated to either a no-rest group, a rest group, or a control group. Subjects in the two training groups trained their elbow flexor muscles by lifting a 6RM weight 6-10 times on 3 d each week for 6 wk. Subjects in the no-rest group performed repeated lifts without resting, whereas subjects in the rest group rested for 30 s between lifts. Both training groups performed the same number of lifts at the same relative intensity. The control group did not train. Subjects who trained without rests experienced significantly greater mean increases in dynamic strength (56.3% +/- 6.8% (SD)) than subjects who trained with rests (41.2% +/- 6.6%), and both training groups experienced significantly greater mean increases in dynamic strength than the control group (19.7% +/- 6.6%). It was concluded that greater short-term strength increases are achieved when subjects are required to lift training weights without resting. These findings suggest that processes associated with fatigue contribute to the strength training stimulus.
Journal of Hand Therapy, 1994
The purpose of this study was to investigate the test-retest reliability of isometric grip streng... more The purpose of this study was to investigate the test-retest reliability of isometric grip strength testing using the Jamar dynamometer. Thirty-three subjects, 16 men (mean age = 37.4 years) and 17 women (mean age = 35.5 years), were assessed on two separate occasions using four methods to determine grip strength score. The methods used were (1) the score of one trial, (2) the mean score of two trials, (3) the mean score of three trials, and (4) the highest score of three trials. All five handle positions of the Jamar dynamometer were used during testing. Although still within the limits of acceptability, position 1 was significantly less reliable when compared with the other handle positions. Because the four methods of determining grip strength score were not significantly different in reliability, it was not possible to recommend any method as being more accurate. To analyze curve shape further, grip strength curves for the strongest and weakest men and women were compared by transforming points on the curves into percentages of the maximum value. Transformed curves for both strong and weak subjects were almost identical, indicating that, for this sample, "flattening" of the grip strength curves was a function of weak grip. The present data do not support the use of raw score curve shape as an indicator of sincerity of effort during grip strength testing.
The Journal of Physiology, 1977
1. End-plate potentials produced by brief trains of action potentials (5-7 at 50-100 Hz) were rec... more 1. End-plate potentials produced by brief trains of action potentials (5-7 at 50-100 Hz) were recorded at toad sciatic-sartorius neuromuscular junctions. When transmitter secretion was depressed in solutions containing magnesium, the increase in amplitude (growth pattern) of successive end-plate potentials was greater than could be accounted for by arithmetic summation of facilitation (arithmetic model) as proposed by Mallart & Martin (1967). 3. With e.p.p.s of normal quantal content or in solutions in which the calcium concentration was lowered, growth patterns were occasionally reasonably close to those predicted by the arithmetic model but there was always some degree of disparity. 4. A simple, two-step, kinetic model is described which is more consistent with the varied growth patterns of end-plate potentials that have been recorded. The model can predict growth patterns of e.p.p.s with high or with low quantal content.
British Journal of Pharmacology, 1973
1. Manganese, at low concentrations (05-20 mM), blocks neuromuscular transmission in toads. Endpl... more 1. Manganese, at low concentrations (05-20 mM), blocks neuromuscular transmission in toads. Endplate potentials (e.p.ps) are reduced in amplitude but the amplitude of miniature endplate potentials (m.e.p.ps) is, if anything, increased. 2. The release of transmitter by an action potential is reduced in solutions containing Mn, but is still well described by the Poisson equation. 3. Log-log plots of e.p.p. quantal content (m) against [Ca] have a mean gradient of 3 73, and a model based on the cooperative action of four calcium ions in excitation-secretion coupling, and competitive inhibition by Mn, was constructed. The model, with its exponent of 4, is shown in fact to predict gradients of less than four for log-log plots of m against [Ca]. 4. The assumption of competitive inhibition by Mn was supported by modified Lineweaver-Burk plots of magainst 1 /[Ca]. The mean dissociation constants for Ca and Mn were 1-3 mm and 0-15 mm respectively. From the model, an upper estimate of the density of calcium ' receptor sites ' of 30 per square micron of nerve terminal was obtained. 5. In contrast to its inhibitory effect on evoked release, Mn increases the spontaneous release of transmitter. It is suggested that Mn may increase m.e.p.p. frequency by releasing Ca from an intracellular store.
Respiration Physiology, 2000
Periaqueductal gray (PAG) and nucleus tractus solitarius (NTS) are important centres for regulati... more Periaqueductal gray (PAG) and nucleus tractus solitarius (NTS) are important centres for regulation of cardiorespiratory function in cats. We aimed to study the effects of specific PAG stimulation on cardiorespiratory parameters in the rat. Microinjection of D,L-homocysteic acid (DLH) into dorsolateral PAG of anaesthetised rats, led to: marked increases in respiratory frequency (RF) and amplitude of diaphragmatic electromyogram, decreases in inspiratory and expiratory durations, and increased blood pressure and heart rate. Following injection of propranolol (150 pmol, 30 nl), a beta-adrenergic antagonist, into the commissural subnucleus of NTS, the DLH-induced increase in RF was markedly attenuated. Inspiratory neurones (late I cells) in NTS were excited upon stimulation of PAG and their increased activity was accompanied by increased RF. The changes in activity of the late I cells in response to stimulation of dorsolateral PAG provide physiological evidence of a link, possibly noradrenergic, between the two nuclei and involvement of the NTS in control of respiratory functions orchestrated by the PAG.
Journal of voice : official journal of the Voice Foundation, 2021
Journal of Voice
In the cat four different types of vocalization, mews, howls, cries, and hisses were generated by... more In the cat four different types of vocalization, mews, howls, cries, and hisses were generated by microstimulation in different parts of the periaqueductal gray (PAG). While mews imply positive vocal expressions, howls, hisses, and cries represent negative vocal expressions. In the intermediate PAG, mews were generated in the lateral column, howls, and hisses in the ventrolateral column. Cries were generated in two other regions, the lateral column of the rostral PAG and the ventrolateral column of the caudal PAG. In order to define the specific motor patterns of the mews, howls, and cries, the following muscles were recorded during these vocalizations; larynx (cricothyroid, thyroarytenoid, and posterior cricoarytenoid), tongue (genioglossus), jaw (digastric), and respiration muscles (diaphragm, internal intercostal, external, and internal abdominal oblique). During these mews, howls, and cries we analyzed the frequency, intensity, activation cascades power density, turns, and amplitude analysis of the electromyograms (EMGs). It appeared that each type of vocalization consists of a specific circumscribed motor coordination. The nucleus retroambiguus (NRA) in the caudal medulla is known to serve as the final premotor interneuronal output system for vocalization. Although neurochemical microstimulation in the NRA itself also generated vocalizations, they only consisted of guttural sounds, the EMGs of which involved only small parts of the EMGs of the mews, howls, and cries generated by neurochemical stimulation in the PAG. These results demonstrate that positive and negative vocalizations are generated in different parts of the PAG. These parts have access to different groups of premotoneurons in the NRA, that, in turn, have access to different groups of motoneurons in the brainstem and spinal cord, resulting in different vocalizations. The findings would serve a valuable model for diagnostic assessment of voice disorders in humans.
Journal of Comparative Neurology
The nucleus retroambiguus (NRA) is a neuronal cell group in the medullary ventrolateral tegmentum... more The nucleus retroambiguus (NRA) is a neuronal cell group in the medullary ventrolateral tegmentum, rostrocaudally between the obex and the first cervical spinal segment. NRA neurons are premotor interneurons with direct projections to the motoneurons of soft palate, pharynx, and larynx in the nucleus ambiguus in the lateral medulla as well as to the motoneurons in the spinal cord innervating diaphragm, abdominal, and pelvic floor muscles and the lumbosacral motoneurons generating sexual posture. These NRA premotor interneurons receive very strong projections from the periaqueductal gray (PAG) in the context of basic survival mechanisms as fight, flight, freezing, sound production, and sexual behavior. In the present study in rat we investigated the physiological motor patterns generated by NRA neurons, as the result of vagal, peripheral chemosensory, and nociceptive stimulation. The results show that the NRA contains phasic respiratory modulated neurons, as well as nonphasic tonically modulated neurons. Stimulation in the various rostrocaudal levels of the NRA generates site-specific laryngeal, respiratory, abdominal, and pelvic floor motor activities. Vagal and peripheral chemosensory stimulation induces both excitatory and inhibitory modulation of phasic NRA-neurons, while peripheral chemosensory and nociceptive stimulation causes excitation and inhibition of nonphasic NRA-neurons. These results are in agreement with the concept that the NRA represents a multifunctional group of neurons involved in the output of the emotional motor system, such as vomiting, vocalization, mating, and changes in respiration.
Ergonomics, Mar 27, 2007
The use of measures of strength variability as a means of determining sincerity of effort is beco... more The use of measures of strength variability as a means of determining sincerity of effort is becoming a more common practice, particularly in medico-legal and rehabilitation settings. The stability of such variability measures, however, has not been documented. This research investigated, in two studies, the trial-to-trial variability of grip strength under maximal and submaximal effort conditions. In the first study, 63 subjects were asked to give 100% grip effort, and in the second study 40 subjects from the original group were asked to give 50% grip effort. The Jamar hand dynamometer was used to measure grip strength in both experiments, and a coefficient of variation (CV) was calculated for every three repeat measures at each handle position. Testing was conducted on two separate occasions for both experiments. Although the interoccasion reliability of grip strength was very high, in comparison, the CV was not stable over test occasions, with interoccasion reliability indices close to zero. Factors significantly influencing CV were effort level, with submaximal effort producing larger CVs, and gender, with females having greater strength variability. If the rule is applied that one or more CVs above the 7.5% cut-off value could indicate submaximal effort, then for this sample of subjects giving maximal effort, 97% of females and 64% of males would be misclassified. Applying a single CV classification cut-off value to a mixed sample of subjects appears to unfairly discriminate against the females. Further research into the factors associated with high CV values is essential before the CV can be used with any confidence in a clinical setting as a method for determining sincerity of effort.
The Journal of Physiology, 1974
1. The time dependence of the increase in amplitude (facilitation) of a second end-plate potentia... more 1. The time dependence of the increase in amplitude (facilitation) of a second end-plate potential (e.p.p.) elicited within 10-100 msec of a preceding e.p.p. was examined at neuromuscular junctions in sartorius muscles of toads. Facilitation was defined by two characteristics, initial facilitation and the time constant of its exponential decay. 2. The time constant of decay of facilitation was longer at lower temperatures and the Q10 was 4'3 in the range 10-250 C. There was no significant effect of temperature on initial facilitation. 3. Ouabain (104-10-3 M), lithium substitution for sodium, sodium azide (5 mM) and N-ethylmaleimide (NEM, 0.1 mm) initially had no effect on initial facilitation or the decay of facilitation. After some time, they all caused a longer time constant of decay of facilitation and a depression of initial facilitation. 4. It was concluded that the decay of facilitation is not directly dependent on active transport of sodium ions, calcium efflux, ATP-dependent movements of calcium or mitochondrial uptake of calcium following an action potential. 5. Ouabain, lithium, sodium azide, and NEM all caused an increase in transmitter release. This effect, and the late effects on facilitation, were thought to be due to an increase in intracellular calcium concentration in nerve terminals. 6. No relationship was found between the quantal content of e.p.p.s (range, 0.8-100) and initial facilitation, or the time constant of decay of facilitation. 7. Substitution of strontium for calcium ions caused a marked prolongation of the time constant of decay of facilitation, and a depression of initial facilitation. 8. The results were consistent with the hypothesis that the time 27 PH Y 239 RON J. BALNAVE AND PETER W. GAGE constant of decay of facilitation is related to the rate of disappearance of an ' active' complex of calcium (CaA) which, of itself, is not sufficient for transmitter release. It is suggested that an action potential produces CaA which decays with the time constant of facilitation and CaS, a short-life complex of calcium which decays with the time constant of the phasic release of transmitter. The release of transmitter is proportional to some function of [CaA] and [CaS].
Advances in experimental medicine and biology, 2004
... Page 6. 140 HHSubramanian et aL 6 TP (cmH 0 o c, 7 D "J EO . . . . . 10s DLH Figure 6. D... more ... Page 6. 140 HHSubramanian et aL 6 TP (cmH 0 o c, 7 D "J EO . . . . . 10s DLH Figure 6. DLH into the NRA. TP: Tracheal Pressure, CT: Cricothyroid EMG, D: Diaphragm EMG, EO: External Oblique. ... Journal of Neurophysiology, 72, 1337-56. 7. Li, ZY, Xia, BL, Huang, CJ, 1992. ...
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 1984
Miniature end plate currents (MEPCs) were recorded with focal extracellular electrodes from white... more Miniature end plate currents (MEPCs) were recorded with focal extracellular electrodes from white extraocular muscle fibres of a marine teleost fish,Trachurus novaezelandiae, over a temperature range of 5 °C to 27 °C.1.Teleost MEPCs rose rapidly, attaining a maximum amplitude of 250–500 µV, withTGof about 150 µs at 15 °C (Figs. 1, 2).2.Decay of MEPCs was exponential, with t=1 ms at
Respiratory Research, 2001
Brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor are required si... more Brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor are required simultaneously for survival of dopaminergic primary sensory neurons in vivo.
Respiratory Research, 2001
Brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor are required si... more Brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor are required simultaneously for survival of dopaminergic primary sensory neurons in vivo.
Advances in Experimental Medicine and Biology, 2008
Journal of Neuroscience, 2008
The midbrain periaqueductal gray (PAG) organizes basic survival behavior, which includes respirat... more The midbrain periaqueductal gray (PAG) organizes basic survival behavior, which includes respiration. How the PAG controls respiration is not known. We studied the PAG control of respiration by injecting D,L-homocysteic acid in the PAG in unanesthetized precollicularly decerebrated cats. Injections in different parts of the PAG caused different respiratory effects. Stimulation in the dorsomedial PAG induced slow and deep breathing and dyspnea. Stimulation in the dorsolateral PAG resulted in active breathing and tachypnea consistent with the respiratory changes during fright and flight. Stimulation in the medial part of lateral PAG caused inspiratory apneusis. Stimulation in lateral parts of the lateral and ventrolateral PAG produced respiratory changes associated with vocalization (mews, alternating mews and hisses, or hisses). D,L-Homocysteic acid injections in the caudal ventrolateral PAG induced irregular breathing. These results demonstrate that the PAG exerts a strong influence on respiration, suggesting that it serves as the behavioral modulator of breathing.
Safety Science, 1997
Occupational rehabilitation professionals have for many years recognised the need to develop meth... more Occupational rehabilitation professionals have for many years recognised the need to develop methods to determine whether a genuinely maximal effort is being given during clinical strength testing. A number of different sincerity of effort tests have been devised in an attempt to satisfy this need, however, in most cases the accuracy and reliability of these tests have not been adequately researched. This article reviews three of the most commonly-used sincerity of effort tests.
Respiratory Physiology & Neurobiology, 2007
The purpose of this study was to examine the effect of mechanical ventilation (MV) on inherent br... more The purpose of this study was to examine the effect of mechanical ventilation (MV) on inherent breathing and on dorsal brainstem nucleus tractus solitarius (NTS) respiratory cell function. In pentobarbitone-anaesthetised rats, application of MV at combined high frequencies and volumes (representing threshold levels) produced apnea. The apnea persisted as long as MV was maintained at or above the threshold frequency and volume. Following removal of MV, inherent breathing did not resume immediately, with the diaphragm exhibiting post-mechanical ventilation apnea. The fall in arterial P CO 2 (Pa CO 2) levels evoked by MV-engendered hyperventilation was shown not to be the trigger for initiation of apnea. MV-induced apnea was immediately reversed by bilateral vagotomy. Further, MV-induced apnea could not be evoked in bilaterally vagotomized animals suggesting that vagal feedback is the critical pathway for its initiation. NTS inspiratory neurones were inhibited during both MV-induced apnea and post-mechanical ventilation apnea, implying the involvement of central neural mechanisms in mediating this effect.
Respiratory Physiology & Neurobiology, 2013
Corrigendum Corrigendum to "Roles of periaqueductal gray and nucleus tractus solitarius in cardio... more Corrigendum Corrigendum to "Roles of periaqueductal gray and nucleus tractus solitarius in cardiorespiratory function in the rat brainstem" [Respir. Physiol. 120 (3) (2000) 185-195]
Medicine & Science in Sports & Exercise, 1994
To investigate the role of fatigue in strength training, strength increases produced by a trainin... more To investigate the role of fatigue in strength training, strength increases produced by a training protocol in which subjects rested between contractions were compared with those produced when subjects did not rest. Forty-two healthy subjects were randomly allocated to either a no-rest group, a rest group, or a control group. Subjects in the two training groups trained their elbow flexor muscles by lifting a 6RM weight 6-10 times on 3 d each week for 6 wk. Subjects in the no-rest group performed repeated lifts without resting, whereas subjects in the rest group rested for 30 s between lifts. Both training groups performed the same number of lifts at the same relative intensity. The control group did not train. Subjects who trained without rests experienced significantly greater mean increases in dynamic strength (56.3% +/- 6.8% (SD)) than subjects who trained with rests (41.2% +/- 6.6%), and both training groups experienced significantly greater mean increases in dynamic strength than the control group (19.7% +/- 6.6%). It was concluded that greater short-term strength increases are achieved when subjects are required to lift training weights without resting. These findings suggest that processes associated with fatigue contribute to the strength training stimulus.
Journal of Hand Therapy, 1994
The purpose of this study was to investigate the test-retest reliability of isometric grip streng... more The purpose of this study was to investigate the test-retest reliability of isometric grip strength testing using the Jamar dynamometer. Thirty-three subjects, 16 men (mean age = 37.4 years) and 17 women (mean age = 35.5 years), were assessed on two separate occasions using four methods to determine grip strength score. The methods used were (1) the score of one trial, (2) the mean score of two trials, (3) the mean score of three trials, and (4) the highest score of three trials. All five handle positions of the Jamar dynamometer were used during testing. Although still within the limits of acceptability, position 1 was significantly less reliable when compared with the other handle positions. Because the four methods of determining grip strength score were not significantly different in reliability, it was not possible to recommend any method as being more accurate. To analyze curve shape further, grip strength curves for the strongest and weakest men and women were compared by transforming points on the curves into percentages of the maximum value. Transformed curves for both strong and weak subjects were almost identical, indicating that, for this sample, "flattening" of the grip strength curves was a function of weak grip. The present data do not support the use of raw score curve shape as an indicator of sincerity of effort during grip strength testing.