Clinical Efficacy of Biosimilar Switch of Adalimumab for Management of Uveitis

BACKGROUND

Adalimumab has demonstrated efficacy in non-infectious uveitis. With the introduction of biosimilar agents such as Amgevita, we aimed to quantify efficacy and tolerability compared to Humira in a multi-centre UK cohort.

METHODS

Patients identified from tertiary uveitis clinics in 3 centres, after institution-mandated switching was implemented.

RESULTS

Data collected for 102 patients, aged 2-75 years, with 185 active eyes. Following switch, rates of uveitis flare were not significantly different (13 events before, 21 after, p = .132). Rates of elevated intraocular pressure were decreased (32 before, 25 afterwards, p = .006) and dosing of oral and intra-ocular steroids was stable. Twenty-four patients (24%) requested to return to Humira, commonly due to pain from injection or technical difficulty with the device.

CONCLUSION

Amgevita is safe and effective for inflammatory uveitis with non-inferiority to Humira. Significant numbers of patients requested to switch back due to side effects including injection site reactions.

Altered regional brain T2 relaxation times in individuals with chronic orofacial neuropathic pain

The neural mechanisms underlying the development and maintenance of chronic pain following nerve injury remain unclear. There is growing evidence that chronic neuropathic pain is associated with altered thalamic firing patterns, thalamocortical dysrhythmia and altered infra-slow oscillations in ascending pain pathways. Preclinical and post-mortem human studies have revealed that neuropathic pain is associated with prolonged astrocyte activation in the dorsal horn and we have suggested that this may result in altered gliotransmission, which results in altered resting neural rhythm in the ascending pain pathway. Evidence of astrocyte activation above the level of the dorsal horn in living humans is lacking and direct measurement of astrocyte activation in living humans is not possible, however, there is evidence that regional alterations in T2 relaxation times are indicative of astrogliosis. The aim of this study was to use T2 relaxometry to explore regional brain anatomy of the ascending pain pathway in individuals with chronic orofacial neuropathic pain. We found that in individuals with trigeminal neuropathic pain, decreases in T2 relaxation times occurred in the region of the spinal trigeminal nucleus and primary somatosensory cortex, as well as in higher order processing regions such as the dorsolateral prefrontal, cingulate and hippocampal/parahippocampal cortices. We speculate that these regional changes in T2 relaxation times reflect prolonged astrocyte activation, which results in altered brain rhythm and ultimately the constant perception of pain. Blocking prolonged astrocyte activation may be effective in preventing and even reversing the development of chronic pain following neural injury.

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Reduced T2 relaxation time in the ascending pain pathway in chronic orofacial pain.

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These reductions may be associated with astrogliosis.

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Increase astrocyte activity associated with chronic orofacial pain.

Disruption of default mode network dynamics in acute and chronic pain states

It has been proposed that pain competes with other attention-demanding stimuli for cognitive resources, and many chronic pain patients display significant attention and mental flexibility deficits. These alterations may result from disruptions in the functioning of the default mode network (DMN) which plays a critical role in attention, memory, prospection and self-processing, and recent investigations have found alterations in DMN function in multiple chronic pain conditions. Whilst it has been proposed that these DMN alterations are a characteristic of pain that is chronic in nature, we recently reported altered oscillatory activity in the DMN during an acute, 5  minute noxious stimulus in healthy control subjects. We therefore hypothesize that altered DMN activity patterns will not be restricted to those in chronic pain but instead will also occur in healthy individuals during tonic noxious stimuli. We used functional magnetic resonance imaging to measure resting state infra-slow oscillatory activity and functional connectivity in patients with chronic orofacial pain at rest and in healthy controls during a 20-minute tonic pain stimulus. We found decreases in oscillatory activity in key regions of the DMN in patients with chronic pain, as well as in healthy controls during tonic pain in addition to changes in functional connectivity between the posterior cingulate cortex and areas of the DMN in both groups. The results show that similar alterations in DMN function occur in healthy individuals during acute noxious stimuli as well as in individuals with chronic pain. These DMN changes may reflect the presence of pain per se and may underlie alterations in attentional processes that occur in the presence of pain.

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Default mode network dynamics were measured in chronic and acute pain.

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Altered infra-slow activity and connectivity occurred in chronic and acute pain.

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Default mode network changes characterize pain per se.

The medial pterygoid muscle: a stabiliser of horizontal jaw movement

There is limited information of the normal function of the human medial pterygoid muscle (MPt). The aims were to determine whether (i) the MPt is active throughout horizontal jaw movements with the teeth apart and (ii) whether single motor units (SMUs) are active during horizontal and opening-closing jaw movements. Intramuscular electrodes were placed in the right MPt of 18 participants who performed five teeth-apart tasks: (i) postural position, (ii) ipsilateral (i.e. right) jaw movement, (iii) contralateral movement, (iv) protrusive movement and (v) opening-closing movement. Movement tasks were guided by a target and were divided into BEFORE, OUT, HOLDING, RETURN and AFTER phases according to the movement trajectories recorded by a jaw tracking system. Increased EMG activity was consistently found in the OUT, HOLDING and RETURN phases of the contralateral and protrusive movement tasks. An increased RETURN phase activity in the ipsilateral task indicates an important role for the MPt in the contralateral force vector. Of the 14 SMUs active in the opening-closing task, 64% were also active in at least one horizontal task. There were tonically active SMUs at the postural jaw position in 44% of participants. These new data point to an important role for the MPt in the fine control of low forces as required for stabilisation of vertical mandibular position not only to maintain postural position, but also throughout horizontal jaw movements with the teeth apart. These findings provide baseline information for future investigations of the possible role of this muscle in oro-facial pain conditions.

Functional Activity of Superior Head of Human Lateral Pterygoid Muscle during Isometric Force

There is controversy as to the jaw tasks for which the superior head of the human lateral pterygoid muscle (SHLP) becomes active. The aim was to describe the functional activities of SHLP single motor units (SMUs) during horizontal isometric force tasks. In 11 subjects, 48 SMUs were recorded from computer-tomography-verified SHLP sites during generation of horizontal isometric force in the contralateral (CL), protrusive (P), and ipsilateral (IL) directions and intermediate directions (CL-P, IL-P). In eight subjects, SHLP SMUs were active in CL, CL-P, and P. Qualitatively, SHLP EMG activity increased with increased isometric force. Forty-two SMUs were active in directions other than IL; 6 exhibited activity at IL and other directions. The similarity of these data to previous human lateral pterygoid (IHLP) data supports the notion that SHLP and IHLP should be regarded as a single muscle, with activities shaded according to the biomechanical demands of the task.

Effect of experimental anterior temporalis muscle pain on jaw movements

To test the hypotheses that experimental noxious stimulation of the anterior temporalis muscle results in significant decreases in jaw movement amplitude and velocity, and there are significant correlations between scores of mood or pain-related cognitions and amplitude and velocity. The jaw movements of 14 asymptomatic participants were recorded during standardised open/close jaw movements and free and standardised chewing tasks. Tonic infusion of hypertonic saline into the right anterior temporalis muscle maintained pain intensity between 40 and 60 mm on a 100-mm visual analogue scale. Tasks were performed in a single session in the following sequence: baseline condition, test 1 condition (during hypertonic or isotonic saline infusion), test 2 condition (during saline infusion) (10-min rest between conditions). Participants completed the Depression, Anxiety and Stress Scale (DASS-21) and the Pain Catastrophizing Scale (PCS). Amplitude and velocity of opening and closing were compared between conditions with a repeated-measures analysis of variance (anova), and Spearman's rank correlation coefficient explored correlations; statistical significance: P < 0·05. For any of the three tasks, there were no significant differences in kinematic variables between any condition and no significant correlations between DASS-21 or PCS scores and kinematic variables during hypertonic saline infusion. The absence of a significant reduction in velocity or amplitude of open/close or chewing jaw movements during experimental temporalis muscle pain is not consistent with the Pain Adaptation Model proposing decreases in kinematic measures in pain. The lack of significant correlations between psychological variables and measures of jaw movement may reflect the low scores reported by our study sample.

A retrospective epidemiological analysis of risk factors for a primary necropsy diagnosis of bovine respiratory disease

Bovine respiratory disease (BRD) is a multifactorial disease and the primary cause of both bovine morbidity and mortality in Ireland. The risk factors associated with a primary necropsy diagnosis of BRD among cattle in the traditional (non-feedlot) husbandry systems prevalent in Ireland have not been investigated previously. The aim of this case-control study was to investigate those risk factors among cattle of all ages over an 8 year period. A total of 3,090 BRD cases and 5,236 controls were matched by submitting veterinary practitioner. Univariable and multivariable analyses were performed to examine the association of selected animallevel, herd-level and environmental risk factors with case or control status using a conditional logistical regression model. Male cattle aged more than 31 days were significantly more likely to record a primary necropsy diagnosis of BRD than female cattle. Older cattle of both sexes were at increased odds of a BRD necropsy diagnosis than younger calves with the exception of female cattle aged greater than 165 days. The risk of a primary necropsy diagnosis of BRD increased with increasing herd size and decreased with increasing time in days since the last animal movement into the submitting herd. There were significantly reduced odds of a primary necropsy diagnosis of BRD in the summer (June to August) when compared with the autumn (September to November). These findings identify significant risk factors for a necropsy diagnosis of BRD under non-feedlot-type husbandry conditions.

Isotonic resistance jaw exercise alters jaw muscle coordination during jaw movements

The aim was to investigate the effects of isotonic resistance exercise on the electro-myographic (EMG) activity of the jaw muscles during standardised jaw movements. In 12 asymptomatic adults surface EMG activity was recorded from the anterior temporalis and masseter muscles bilaterally and the right anterior digastric muscle during right lateral jaw movements that tracked a target. Participants were randomly assigned to a Control group or an Exercise group. Jaw movement and EMG activity were collected (i) at baseline, before the exercise task (pre-exercise); (ii) immediately after the exercise task (isotonic resistance at 60% MVC against right lateral jaw movements); (iii) after 4 weeks of a home-based exercise programme; and, (iv) at 8-weeks follow-up. There were no significant within-subject or between-group differences in the velocity and amplitude of the right lateral jaw movements either within or between data collection sessions (P > 0.05). However, over the 8 weeks of the study, three of the tested EMG variables (EMG Duration, Time to Peak EMG from EMG Onset, and Time to Peak EMG activity relative to Movement Onset) showed significant (P < 0.05) differences in the five tested muscles. Many of the significant changes occurred in the Control group, while the Exercise group tended to maintain the majority of the tested variables at pre-exercise baseline values. The data suggest a level of variability between recording sessions in the recruitment patterns of some of the muscles of mastication for the production of the same right lateral jaw movement and that isotonic resistance exercise may reduce this variability.

Noxious Lingual Stimulation Influences the Excitability of the Face Primary Motor Cerebral Cortex (Face MI) in the Rat

The mechanisms whereby orofacial pain affects motor function are poorly understood. The aims were to determine whether 1) lingual algesic chemical stimulation affected face primary motor cerebral cortex (face MI) excitability defined by intracortical microstimulation (ICMS); and 2) any such effects were limited to the motor efferent MI zones driving muscles in the vicinity of the noxious stimulus. Ketamine-anesthetized Sprague–Dawley male rats were implanted with electromyographic (EMG) electrodes into anterior digastric, masseter, and genioglossus muscles. In 38 rats, three microelectrodes were located in left face MI at ICMS-defined sites for evoking digastric and/or genioglossus responses. ICMS thresholds for evoking EMG activity from each site were determined every 15 min for 1 h, then the right anterior tongue was infused (20 μl, 120 μl/h) with glutamate (1.0 M, n = 18) or isotonic saline ( n = 7). Subsequently, ICMS thresholds were determined every 15 min for 4 h. In intact control rats ( n = 13), ICMS thresholds were recorded over 5 h. Only left and right genioglossus ICMS thresholds were significantly increased (≤350%) in the glutamate infusion group compared with intact and isotonic saline groups ( P < 0.05). These dramatic effects of glutamate on ICMS-evoked genioglossus activity contrast with its weak effects only on right genioglossus activity evoked from the internal capsule or hypoglossal nucleus. This is the first documentation that intraoral noxious stimulation results in prolonged neuroplastic changes manifested as a decrease in face MI excitability. These changes appear to occur predominantly in those parts of face MI that provide motor output to the orofacial region receiving the noxious stimulation.

A working-side change to lateral tooth guidance increases lateral pterygoid muscle activity

The inferior head of lateral pterygoid (IHLP) is thought to play a critical role in the generation and control of lateral jaw movements.

AIM

The aim was to test the hypothesis that a change to the lateral tooth guidance (working-side occlusal alteration, OA) results in a significant change in the electromyographic (EMG) activity of the IHLP during standardised lateral jaw movements (laterotrusion) tracked by a jaw-tracking system.

METHODS

Ten trials of right laterotrusion were repeated under: control 1 (before occlusal alteration), OA (after occlusal alteration placement), and control 2 (after occlusal alteration removal) conditions in 14 subjects while recording left IHLP, bilateral anterior and posterior temporalis, masseter and submandibular muscles.

RESULTS

IHLP activity was significantly (p<0.05) increased with the occlusal alteration during the outgoing (movement from intercuspal position to approximately 5mm right) and return phases of laterotrusion. The other muscles demonstrated no change or a significant decrease in activity.

CONCLUSIONS

These findings suggest that a change to the occlusion on the working-side in the form of a steeper guidance necessitates an increase in IHLP activity to move the mandible down the steeper guidance. It must be emphasised that these data cannot be used as justification for occlusal therapy.

Density and structural changes in the bone of growing rats after weekly alendronate administration with and without a methotrexate challenge

Alendronate (ALN) and other bisphosphonates have been used successfully in pediatric patients with osteopenia secondary to connective tissue diseases. Loss of growth in height has not been reported, but concerns remain regarding the effect of these potent antiresorptive agents when used in children and adolescents. High-dose methotrexate (MTX) and other chemotherapy drugs have been implicated in osteoporosis and a high fracture incidence in survivors of childhood cancers and are also associated with osteopenia in adult animals. The effect of high dose MTX on bone density during rapid skeletal growth, however, has not been widely studied, nor has the potentially therapeutic effect of bisphosphonates in this setting. We examined the effects of ALN and MTX administration, alone and in combination, on bone density, morphology, mechanical strength, and longitudinal growth in normal growing rats. Sprague-Dawley rats were given ALN once weekly (0.3 mg/kg) from 5 to 11 weeks of age, with and without a course of methotrexate (MTX) given daily in weeks 1 and 3 (0.75 mg/kg/day). Twenty-four animals were randomly divided into four groups: Control (vehicle), ALN alone, ALN + MTX, and MTX alone. After 6 weeks, the femora, tibiae, and lumbar spine were studied by dual-energy X-ray absorptiometry, peripheral quantitative computed tomography, mechanical strength testing, microradiography, light microscopy, and by determination of ash weights and bone lengths. ALN treatment increased bone mineral density (BMD) by 23% to 68%. The largest increases in the femur occurred in the distal third where endochondral bone growth was greatest and included large increases in trabecular bone and total cross-sectional area. ALN + MTX produced similar effects to ALN alone. MTX only reduced BMD by 8% in the vertebrae, but not significantly at other sites. MTX also led to femoral length reductions of 2.9%. The small reductions in BMD due to MTX were overwhelmed by the increases due to ALN, whereas the length loss was unaffected. Transverse density banding corresponding to weekly ALN administrations were clearly evident radiographically throughout the growing skeleton, likely due to decreased resorption and possibly increased mineralization in the bands. ALN or ALN + MTX treatment also led to increases in mechanical strength in the femora. Although MTX administration during growth leads to some BMD reduction, ALN given with MTX eliminates this reduction and in fact bone density and strength increase above control levels.

Ipsilateral interferences and working-side condylar movements

There is limited knowledge of the effects of the occlusion on temporomandibular joint function.

AIM

The aim was to investigate the influence of a working-side occlusal alteration (OA, i.e. interference) on trajectories of working-side condylar points during standardized lateral jaw movements (laterotrusion) tracked by a jaw-tracking system.

METHODS

Ten trials of right laterotrusion were repeated under: control 1 (before OA), OA (immediately after placement of a working-side interference) and control 2 (immediately after removal of OA) conditions.

RESULTS

During right jaw movement, the paths of the working-side condylar points under OA were significantly more inferior and anterior to those under control at the same amount of mid-incisor-point displacement from the intercuspal position. The OA significantly reduced the rotation of the mandible about the antero-posterior and supero-inferior axes and significantly increased the opening angle. Controls 1 and 2 were not significantly different.

CONCLUSIONS

A working-side interference has an immediate, significant effect on working-side condylar movement.

Impact of annual legume 'break' crops on the yield and quality of canola in comparison with the impact on yield of wheat

This study investigated the yield, oil and protein content of canola in response to alternative single-season legume crops, and compared the yield response with that of wheat. Two field trials were conducted in consecutive years at Wagga Wagga on the South West Slopes of New South Wales. The soil type was Red Kandasol. The legume treatments were field pea and vetch managed for silage production, vetch managed for green manure, a mixture of aerial seeding clovers (Berseem, Arrowleaf, Persian: 6 : 3 : 3) managed for silage, hay or green manure, and field pea and narrow-leaf lupin managed for grain. There was one wheat treatment managed for grain. In terms of growing season rainfall, the rainfall-use efficiency of canola was low and similar to that achieved on farms (5.1 kg/ha.mm rainfall). Yields of canola were less than potential water-limited yields and the canola equivalent wheat yields were less than comparative wheat yields. The constraint(s) on canola yield meant that nitrogen-limited yield potential was not reached, and in contrast to wheat in adjacent plots, there was no relationship between canola seed yield and soil mineral nitrogen available during seedling establishment of canola. However, relative to other legume treatments, antecedent crops of the clover mix depressed yield and total oil content, particularly in one year. It was concluded that under field conditions that constrained canola productivity to that similar to on-farm productivity, wheat may make more efficient use of legume nitrogen than canola. Were canola to be used as the response crop, antecedent legumes of vetch or pea, rather than aerial seeding clover, would give higher potential yield and total oil content of the canola.

Activity of inferior head of human lateral pterygoid muscle during standardized lateral jaw movements

OBJECTIVE

(a) To describe the changes in electromyographic (EMG) activity from selected jaw muscles during a standardized lateral jaw movement with the teeth together, and (b) to investigate the effects on jaw muscle activity of changes in both the rate of lateral jaw movement and the relative magnitude of jaw-closing force.

DESIGN

In 16 healthy volunteers, recordings were made using a jaw-tracking system, of mid-incisor point (MIPT) movements, as well as EMG activity from the contralateral inferior head of the lateral pterygoid muscle (IHLP), and bilateral anterior and posterior temporalis, masseter and submandibular muscles, during lateral jaw movement tasks at two speeds and two closing force levels with the teeth together.

RESULTS

The IHLP was the only muscle to show a consistent increase in activity in association with the outgoing phase of the task and a decrease during the return phase. Under high closing force at slow speed, the EMG activities of the IHLP and bilateral anterior temporalis and masseter muscles were significantly (p < 0.05) higher than those under a low closing force, while there was no significant change (p > 0.05) in bilateral posterior temporalis and submandibular muscles. The change from slow to fast lateral movement at low force did not significantly (p > 0.05) alter the mean activity except for the IHLP (increase in activity) and the contralateral anterior temporalis (decrease in activity).

CONCLUSIONS

The data suggest that the IHLP is one of the principal jaw muscles involved in a lateral jaw movement with the teeth together while the other jaw muscles may play a contributory or facilitatory role.

The human lateral pterygoid muscle: A review of some experimental aspects and possible clinical relevance

The clinical notion that some disturbance to the activity of the lateral pterygoid muscle plays a role in the aetiology of temporomandibular disorders (TMD) is still widely accepted and influences management strategies. However, there is no rigorous scientific evidence to support this clinical notion and the role of the lateral pterygoid muscle in normal function is still controversial. The classically defined functions of each head of the muscle are that the superior head is active on closing, retrusion, and ipsilateral jaw movements, while the inferior head is active on opening, protrusion and contralateral jaw movements. However, recent data indicate that these concepts are too simplistic. For example, recent evidence suggests that parts of the superior head may also be active on opening, protrusion and contralateral jaw movements, and that the superior head may consist of three mediolaterally arranged functional zones. Given these complexities, the proposal that clicking and/or locking conditions arise in the temporomandibular joint through some form of lack of co-ordination between the two heads of the muscle needs re-evaluation. Despite earlier reports to the contrary, both heads of the lateral pterygoid muscle appear to be electrically silent at the postural or resting jaw position, and therefore appear to play no role in the anteroposterior positioning of the jaw at the postural position. An important role has also been demonstrated electromyographically for progressive changes in activity in the inferior head as the direction of horizontal jaw force shifts from one side to the other. This suggests an important role for the lateral pterygoid muscle in the generation of side-to-side and protrusive jaw forces. The lateral pterygoid muscle is likely therefore to play an important role in parafunctional excursive jaw movements and also possibly a role in influencing jaw position in patients where the maxillomandibular relationship records change from session to session. The above data provide new insights into the normal function of the lateral pterygoid muscle. The proposal that the lateral pterygoid muscle plays some role in the aetiology of TMD needs now to be rigorously tested.

Minimal tonic firing rates of human lateral pterygoid single motor units

OBJECTIVE

The minimal tonic firing rates (the lowest firing rates at which motor units fire regularly; MTFR) of single motor units (SMUs) within the lateral pterygoid muscle have not been widely investigated. The aims of this study were (a) to identify MTFR of SMUs within the inferior head (IHLP) and superior head (SHLP) of the lateral pterygoid muscle during horizontal jaw movements, and (b) to determine whether these MTFR vary with movement direction.

METHODS

Twenty subjects moved the jaw to maintain SMU firing at the lowest continuous firing rate. SMU activity was recorded from computer-tomography-verified sites within the IHLP or SHLP.

RESULTS

In the IHLP, the mean (+/-SD) MTFR for contralateral movement (15.6+/-2.3 imp/s; n=22 SMUs) were not significantly different from those during protrusion (16.3+/-3.4 imp/s; n=19). In the SHLP, the mean (+/-SD) MTFR for contralateral, ipsilateral movement, and protrusion were 14.7+/-2.5 imp/s (n=10), 13.2+/-2.1 imp/s (n=8), and 16.2+/-3.7 imp/s (n=2), respectively.

CONCLUSIONS

Lateral pterygoid SMUs have greater MTFR than previously reported in the masseter and IHLP, namely 5-8 and 8-10 imp/s, respectively. The MTFR did not vary with the task within each muscle head.

SIGNIFICANCE

Some physiological properties of lateral pterygoid SMUs may be different from those in other jaw muscles.

Functional heterogeneity in the superior head of the human lateral pterygoid

The activity of the superior head of the human lateral pterygoid muscle (SHLP) is controversial. Given the non-parallel alignment of some SHLP fibers, the SHLP may be capable of differential activation. The aims were to clarify SHLP activity patterns in relation to location within SHLP. In 18 subjects, SHLP single motor units were intramuscularly recorded at computer-tomography-verified sites during horizontal (e.g., protrusion) and vertical (e.g., opening) jaw tasks (recorded by a jaw-tracking device) and at resting postural jaw position. None of 92 units was active at the resting postural position. Medially located units (21) showed activity during contralateral movement, protrusion, and opening; 5 were also active on jaw closing. There was a significant association between unit location and the number of units active during vertical tasks (i.e., jaw closing and clenching). Analysis of the data suggests differential activation within SHLP and raises the possibility of functional heterogeneity within SHLP.

Prevalence of sclerotinia stem rot of canola in New South Wales

Surveys of petal infestation and stem infection conducted in 1998, 1999 and 2000 indicated that Sclerotinia sclerotiorum poses a threat to the Australian canola industry. Inoculum was present throughout all canola-growing regions of New South Wales and the stem disease was widespread throughout southern New South Wales. Percentage petal infestation increased over the 3 years surveyed with values ranging from 0 to 99.4%. The highest petal infestation values were observed in 2000 (maximum of 99.4%, mean of 82.2%), with lower mean values in 1998 (38.4%) and 1999 (49.6%). Stem infection ranged from 0 to 37.5% and most fields had less than 10% stem infection. Stem rot incidence before harvest did not relate to percentage petal infestation determined during flowering. This indicated that factors other than percentage petal infestation were important in influencing stem rot incidence. While there was no relationship between percentage petal infestation and stem rot incidence, stem infection never occurred without prior petal infestation.

Impact of legume 'break' crops on the yield and grain quality of wheat and relationship with soil mineral N and crop N content

The effect of annual 'break' crops on the yield and protein content of wheat was investigated over 3 seasons on a Red Kandasol on the south-western slopes of New South Wales. The 'break' crops included lupin and pea grown for grain, pea and vetch managed for silage, clovers managed for silage or hay, and vetch and clovers managed for green manuring. Wheat was sown for 2 years following the legume year, or canola and wheat followed the legumes. Averaged over 3 experiments the yields of first crop wheat following pea or vetch silage crops were comparable with those after grain pea. Yields following clover forage conservation crops or green manures exceeded those after grain pea by at least 0.41 t/ha; average yield increase after clover green manure was 0.93 t/ha. In one experiment, yields of second crop wheat were greater, by up to 0.37 t/ha, after forage conservation or green manure legume 'breaks' than after grain legumes. In 2 experiments, second crop wheat yields were greater after a first crop of canola than a first crop of wheat. Compared with continuous wheat yield, aggregate mean wheat yield increases were 3.5–4 t/ha following grain legumes, pea, and vetch silage crops, but 5.3–6.3 t/ha following clover forage conservation and green manure crops. However, the relative effects of legume treatments on wheat yield were significantly seasonally dependent. Yield and grain protein variation in wheat after legumes was significantly correlated with variation in mineral N at wheat establishment. However, in one experiment, yield was correlated only with variation in mineral N below the 20-cm soil depth, whereas protein was correlated only with variation in mineral N above the 20 cm soil depth. Yield increases in first crop wheat did not occur at the expense of grain protein.

Impact of legume 'break' crops on the residual amount and distribution of soil mineral nitrogen

Important factors in the successful uptake of grain legumes by cereal growers have been their capacity to increase soil N and control cereal disease, as these have underpinned high yields in following wheat crops. However, alternative 1-year legume crops are required to introduce additional biodiversity and management flexibility for cereal growers. The effects on soil mineral N and potential contribution to soil total N of other legume enterprises were studied. These included vetch (Vicia bengalhensis) or clovers (mix of Trifolium alexandrinum, T.�versiculosum, T. resupinatum) managed for green manure; pea (Pisum sativum), vetch, or clovers managed for silage; and clovers managed for hay. These were compared with pea and lupin (Lupinus angustifolius) managed for grain production. Wheat was also included as a control. The legumes were grown in acidic Red Kandasol soil at Wagga Wagga in southern New South Wales, in 1996, 1997, and 1998. Mineral N was measured in the autumn or winter of seasons 1997 and 1998 respectively. Amounts of stubble residue N were measured in all seasons. The green manure crops, particularly vetch, produced more mineral N than both grain legumes. The forage conservation crops (silage or hay) produced similar amounts of mineral N to grain pea and more than grain lupin. For the grain and green manure legume crops, variation in amounts of mineral N was explained by the total N content of legume stubble residue, but for the forage conservation crops, more mineral N was measured than was predictable from stubble N. The amounts of mineral N at different soil depths differed between legume treatments and experiments (sites and years). Based only on above-ground plant N, the green manure crops contributed more to increasing total soil N than grain legumes; in turn, the grain legumes contributed more than the forage conservation crops. It was concluded that alternative annual legume enterprises to grain legumes may provide at least similar enrichment of soil mineral N early in the following season, and that all annual legume enterprises may accumulate nitrate deep in the soil profile in some seasons.

The role of the human lateral pterygoid muscle in the control of horizontal jaw movements

There is a limited understanding of the normal function of the lateral pterygoid muscle (LP) and the role that this muscle plays in temporomandibular disorders. This article addresses the hypothesis that a major function of the LP is in the control of horizontal jaw movements. The range of fiber alignments suited to generating a major horizontal force vector (magnitude and direction), together with the likelihood of independent activation of subcompartments (that is, functionally heterogeneous zones) within each head, provide the possibility of a finely graded range of force vectors on the condyle to effect the fine control of horizontal jaw movements. This level of control does not appear to extend to the control of resting jaw posture, as recent single motor unit (SMU) data indicate that the LP is inactive with the jaw in the postural jaw position. Available electromyographic data demonstrate graded changes in multiunit and SMU activity with small horizontal jaw displacements at low force levels, a single preferred direction of the SMU firing rate during horizontal isometric jaw tasks, and graded changes in the SMU firing rate with horizontal force magnitude and direction. The evidence suggests that a major function of the LP is in the generation and fine control of the horizontal component of jaw movement by the graded activation of a subset of SMUs within the LP. The data also suggest that the LP is involved in the generation of horizontal force vectors, as required in parafunctional activities and heavy mastication.

Activity in the inferior head of the human lateral pterygoid muscle with different directions of isometric force

The aim was to test the hypothesis that this head of the muscle plays a part in the generation and fine control of horizontal mandibular forces in a range of directions. Electromyographic activity was recorded from the inferior head of the lateral pterygoid of eight individuals during the generation such forces to a target in contralateral, ipsilateral and protrusive directions, and in two intermediate directions (contralateral-protrusive, ipsilateral-protrusive). The mean electromyographic activity and the mean firing rates of 21 single-motor units were significantly affected by direction, with the highest activity being contralateral, and graded decreases occurring as the direction shifted to the ipsilateral. Firing rates were significantly correlated with force magnitude. The data suggest that the inferior head of the human lateral pterygoid is involved in the creation and fine control of mandibular forces in different horizontal directions.

Functional properties of single motor units in the inferior head of human lateral pterygoid muscle: task firing rates

The precise function of the inferior head of the human lateral pterygoid muscle (IHLP) is unclear. The aim of this study was to clarify the normal function of the IHLP. The hypothesis was that an important function of the IHLP is the generation and fine control of horizontal (i.e., anteroposterior and mediolateral) jaw movements. The activities of 50 single motor units (SMUs) were recorded from IHLP (14 subjects) during two- or three-step contralateral movement (n = 36) and/or protrusion (n = 33). Most recording sites were identified by computer tomography. There was a statistically significant overall increase in firing rate as the magnitude of jaw displacement increased between the holding phases (range of increments: 0.3-1.6 mm). The firing rates during the dynamic phases for each unit were significantly greater than those during the previous holding phases but less than those during the subsequent holding phases. For the contralateral step task at the intermediate rate, the cross-correlation coefficients between jaw displacement in the mediolateral axis and the mean firing rate of each unit ranged from r = 0.29 to 0.77; mean +/- SD; r = 0.49 +/- 0.13 (protrusive step task: r = 0.12-0.74, r = 0.44 +/- 0.14 for correlation with anterior-posterior axis). The correlation coefficients at the fast rate during the contralateral step task and the protrusive step task were significantly higher than those at the slow rate. The firing rate change of the SMUs per unit displacement between holding phases was significantly greater for the lower-threshold than for the higher-threshold units during contralateral movement and protrusion. After dividing IHLP into four regions, the SMUs recorded in the superior part exhibited significantly greater mean firing rate changes per unit displacement during protrusion than for the SMUs recorded in the inferior part. Significantly fewer units were related to the protrusive task in the superior-medial part. These data support previously proposed notions of functional heterogeneity within IHLP. The present findings provide further evidence for an involvement of the IHLP in the generation and fine control of horizontal jaw movements.

A method of indirect registration of the coordinates of condylar points with a six-degree-of-freedom jaw tracker

Previous studies have indicated that the location of a condylar point can significantly influence its trajectory. The aim of this investigation was to develop a method of registering the location of radiographically defined condylar points in the coordinate system of a six-degree-of-freedom jaw-tracking device and to determine the accuracy of this method by using a perspex model in one experiment and a dry skull in another. A direct measurement ('the gold standard') of condylar point coordinates in the coordinate system of JAWS3D was done using a three-dimensional (3D) digitizer (MicroScribe-3DX). The indirect measurement used a distributed fiducial marker as the interface between the coordinate system of MicroScribe-3DX (which was used to register the fiducial marker and the JAWS3D coordinate system) and the coordinate system of the CT scans (used to define condyle anatomy and the relation with the fiducial marker). The coordinates of condylar points could then be calculated in the coordinate system of JAWS3D. The results showed that the indirect method could register condylar point coordinates on either side to an accuracy of approximately 0.5 mm.

Effect of timing of pasture grass removal on subsequent take-all incidence and yield in wheat in southern New South Wales

Winter cleaning is the removal of grasses from pasture using selective herbicides applied during winter. We compared the effectiveness of an early (June) and late (July) winter cleaning with an early spring herbicide fallow (September), spring (October) herbicide and no disturbance of the pasture on development of the root disease take-all in the subsequent wheat crop. Experiments were done at 5 sites in the eastern Riverina of New South Wales in 1990 and 1991. The winter clean treatments reduced soil inoculum of Gaeumannomyces graminis var. tritici (Ggt) compared with the other treatments at all sites as measured by a bioassay, with reductions from the undisturbed treatments of 52–79% over 5 sites. The winter clean treatments also significantly reduced the amount of take-all that developed in the subsequent wheat crop by between 52 and 83%. The early and late winter clean treatments increased the number of heads/m2 at 3 and 1 sites, respectively. Dry matter at anthesis was increased by the winter clean treatments at 3 sites. Grain yield was increased by the winter cleaning treatments over the other treatments at the 4 sites harvested, with yield increases of the early winter clean over the undisturbed treatment from 13 to 56%. The autumn bioassay of Ggt was positively correlated with spring take-all and negatively correlated with grain yield of the subsequent wheat crop at each site. However, there was a significant site and site × bioassay interaction so that the autumn bioassay could not be used to predict the amount of take-all that would develop.

The role of the inferior head of the human lateral pterygoid muscle in the generation and control of horizontal mandibular force

The aim was to test the hypothesis that the inferior head (IH) of the human lateral pterygoid muscle (LP) is involved in the generation and fine control of horizontal isometric mandibular force. Although previous studies provided some evidence for this, they had limitations that necessitate a re-examination. In eight participants, electromyographic (EMG) activity was recorded from the IHLP unilaterally, as well as bilateral surface recordings from the masseter (M) and anterior temporalis (AT), and the submandibular group of muscles (SUBM), during the generation of horizontal isometric mandibular force in a direction contralateral to the side of the IHLP recording. Isometric force at 5-8 mm open from the intercuspal position was exerted on a transducer (attached by a bar to the upper teeth) by a rod attached to the lower teeth. Participants tracked a target on a video screen that required 5-s holding periods at each 100 gwt (0.98 N) between 400 gwt (3.92 N) and 800 gwt (7.84 N). The mean of multi-unit EMG activity from all muscles during the most stable 2-s force-holding periods increased significantly with each force increment (GLM repeated measures: P<0.0001). When normalized, the multi-unit data from the IHLP exhibited the steepest rate of increase. The mean firing rates of 21 IHLP single motor units (SMUs) significantly increased with force (GLM repeated measures: P<0.0001). Two SMUs fired in advance of force onset, which suggests a role in force initiation. There were close associations between fluctuations in force and in IHLP SMU firing rates and multi-unit activity, but a similar correspondence was not as clear for the other recorded jaw muscles. These findings suggest that the IHLP is important in the generation and fine control of contralaterally directed, horizontal jaw forces.

Functional properties of single motor units in inferior head of human lateral pterygoid muscle: task relations and thresholds

The aim of this study was to clarify the normal function of the inferior head of the human lateral pterygoid muscle (IHLP). The hypothesis was that an important function of the IHLP is in the fine control of horizontal jaw movements. The activities of 99 single motor units (SMUs) were recorded from IHLP (22 recordings from 16 subjects). Most recording sites were identified by computer tomography (CT). All 99 SMUs were active during contralateral jaw movements with the teeth apart, and protrusive jaw movements with the teeth apart, and 81% (48 of 59 units studied during all 3 tasks) were active during submaximal jaw-opening movements. None were active on maximal ipsilateral or retrusive jaw movements with the teeth apart nor on jaw closing/clenching in intercuspal position; nor were they spontaneously active when the jaw was at the clinically determined postural jaw position. Thresholds of SMUs ranged from <0.2 mm of contralateral or protrusive horizontal displacements to 61-89% of the maximum contralateral or protrusive displacement, respectively. For the 35 units continuously active during the contralateral task, 23 (66%) were recruited within 2 mm of contralateral displacement [25 (63% of 40 units) for protrusion]. Recruitment thresholds (mm) of some of the units were rate dependent with thresholds significantly decreasing with increasing rate of horizontal jaw movement in protrusion and contralateral movements. At eight recording sites where up to six SMUs were able to be discriminated, the average thresholds of successively recruited SMUs were within a 1-mm increment of horizontal jaw displacement. After dividing IHLP into four regions, the SMUs recorded in the superior-medial zone exhibited significantly lower mean threshold values than for the SMUs recorded in the other zones (no units were recorded in the inferior-lateral zone). This provides suggestive evidence supporting previously proposed notions of functional heterogeneity within IHLP. Taken together, the data suggest that specific regions of the IHLP are capable of selective activation in a finely controlled manner to allow the application of the appropriate force vector (magnitude and direction) to effect the required condylar movement needed for the generation and control of horizontal jaw movements.

Functional characteristics of the parallel SI- and SII-projecting neurons of the thalamic ventral posterior nucleus in the marmoset

The functional organization of the primate somatosensory system at thalamocortical levels has been a matter of controversy, in particular, over the extent to which the primary and secondary somatosensory cortical areas, SI and SII, are organized in parallel or serial neural networks for the processing of tactile information. This issue was investigated for the marmoset monkey by recording from 55 single tactile-sensitive neurons in the lateral division of the ventral posterior nucleus of the thalamus (VPL) with a projection to either SI or SII, identified with the use of the antidromic collision technique. Neurons activated from the hand and distal forearm were classified according to their peripheral source of input and characterized in terms of their functional capacities to determine whether the direct thalamic input can account for tactile processing in both SI and SII. Both the SI- and SII-projecting samples contained a slowly adapting (SA) class of neurons, sensitive to static skin displacement, and purely dynamically sensitive tactile neurons that could be subdivided into two classes. One was most sensitive to high-frequency (> or =100 Hz) cutaneous vibration whose input appeared to be derived from Pacinian sources, while the other was sensitive to lower frequency vibration (< or =100 Hz) or trains of rectangular mechanical pulse stimuli, that appeared to receive its input from rapidly adapting (RA) afferent fibers presumed to be associated with intradermal tactile receptors. There appeared to be no systematic differences in functional capacities between SI- and SII-projecting neurons of each of these three classes, based on receptive field characteristics, on the form of stimulus-response relations, and on measures derived from these relations. These measures included threshold and responsiveness values, bandwidths of vibrational sensitivity, and the capacity for responding to cutaneous vibrotactile stimuli with phase-locked, temporally patterned impulse activity. The analysis indicates that low-threshold, high-acuity tactile information is conveyed directly to both SI and SII from overlapping regions within the thalamic VP nucleus. This direct confirmation of a parallel functional projection to both SI and SII in the marmoset is consistent with our separate studies at the cortical level that demonstrate first, that tactile responsiveness in SII largely survives the SI inactivation and second, that SI responsiveness is largely independent of SII. It therefore reinforces the evidence that SI and SII occupy a hierarchically equivalent network for tactile processing.

A method for standardizing jaw displacements in the horizontal plane while recording single motor unit activity in the human lateral pterygoid muscle

The normal function of the lateral pterygoid muscle is not well understood although this muscle is thought to play an important role in the control of jaw and jaw-joint function and is implicated in temporomandibular disorders (TMD). The lack of a validated method for standardization of jaw movement in studies of lateral pterygoid function has contributed to the lack of understanding of the normal function of this muscle. An improved understanding of normal function will allow valid comparisons to be made with TMD patients in order to identify whether purported differences in activity actually exist. This paper describes a methodology for standardizing command jaw movements in the horizontal plane, together with reliable recordings of single-motor-unit (SMU) activity. In six human participants, jaw movements were standardized by having participants track a linear bank of light-emitting diodes (LEDs) aligned on a monitor displaying the mid-incisor point (MIPT). In all participants, the MIPT target (i.e. an illuminated LED) could be tracked, according to a pre-determined criterion, during single- and multiple-step displacements at different rates (1.3--6.5 mm/s at MIPT) and magnitudes (0.65--12 mm) of movement. SMU activity from the superior (SHLP) or inferior (IHLP) head of the lateral pterygoid muscle could be reliably discriminated during repeated trials of these defined tasks. This methodology establishes a reliable technique for characterizing the firing properties of SMUs within the lateral pterygoid, and has implications for analogous studies in other jaw muscles.

The accuracy with which the human condyle can be expressed in the coordinate system of JAWS3D using a unilateral fiducial marker

Previous studies have indicated that the selection of condylar referencing points can significantly influence condylar point trajectories, and the use of radiographically determined condylar points is essential for accurate representation of condylar movement. The aim of this investigation was to determine the accuracy with which the three-dimensional locations of condylar points could be determined in the coordinate system of the JAWS3D tracking device when an ipsilateral fiducial marker is used. A perspex mandible containing condylar radiographic markers was constructed. A JAWS3D target frame and a fiducial marker, supporting radiographic markers, were secured to the perspex mandible. The image data from computer tomography scans of the condyles and fiducial marker, together with photographs of the fiducial marker and the JAWS3D target frame were used to calculate condylar point coordinates in the JAWS3D coordinate system. These data were then compared with the data obtained by direct measurement of the condylar radiographic markers in the JAWS3D coordinates. The results suggest that a unilateral fiducial marker is sufficient to allow the registration of ipsilateral condylar point coordinates to an accuracy of approximately 1.0 mm.

Human lateral pterygoid muscle activity on the return phase of contralateral and protrusive jaw movements

Normal function of the lateral pterygoid muscle is not well understood. The principal aim of this study was to determine whether there is a progressive decrease in lateral pterygoid activity as the condyle moves posteriorly and superiorly during the return phase of a contralateral or protrusive jaw movement, as would be expected if the muscle is involved in controlling or stabilizing the condyle during the return phase of these movements. In seven humans, electromyographic activity was recorded in the superior (SHLP) and inferior (IHLP) heads of the lateral pterygoid, the masseter, anterior temporal, posterior temporal and submandibular group of muscles, together with condylar movement, during contralateral and protrusive jaw movement. In most individuals, there was a progressive decrease in rectified and smoothed IHLP activity in relation to condylar movement during the return phase of contralateral and protrusive jaw movement. However, this pattern usually was not seen when SHLP activity was studied in relation to condylar movement. Further, there was a high correlation coefficient between condylar displacement and the rectified and smoothed IHLP and anterior temporal muscle activities during the return phase of contralateral or protrusive jaw movement, while SHLP presented a much lower correlation. For example, the mean (+/-SD) correlation coefficient between posterior condylar movement (along anteroposterior axis) and IHLP activity during the return phase of a protrusive jaw movement was -0.73+/-0.36 (for contralateral movement: -0.71+/-0.56), for the anterior temporal 0.69+/-0.21 (contralateral: 0.81+/-0.09), and for the submandibular muscles, -0. 77+/-0.15 (contralateral: -0.34+/-0.71). For the SHLP, masseter and posterior temporal, values were -0.34+/-0.61 (contralateral: -0. 48+/-0.37), -0.24+/-0.57 (contralateral: 0.16+/-0.80), and 0.16+/-0. 77 (contralateral: 0.64+/-0.14), respectively. These findings suggest an important role for the IHLP and anterior temporal in controlling the movement of the condyle to the glenoid fossa on the return phase of contralateral and protrusive jaw movements. Further studies are needed to clarify the function of the lateral pterygoid muscle during these and other jaw movements.

The effect of nitrous oxide on hearing

There is a belief that the administration of nitrous oxide (N2O) increases hearing acuity. This increase can be interpreted as hearing low intensity sounds more loudly. This study examined auditory threshold levels, acoustic impedance, acoustic perception, memory, and discrimination to determine if hearing was altered by end-tidal 10% or 20% nitrous oxide. Subjects also qualitatively interpreted three intensity levels using a subjective intensity test. Observations were made in the breathing mediums of room air in the control stages (Stages 1 and 4), compared to N2O and supplemental oxygen (Stages 2 and 3), in 16 human subjects in a quiet room. Breathing end-tidal 10% and 20% N2O significantly increased middle ear pressure, and produced a significant effect on the subjective interpretation of a sound's intensity. There was no significant effect on auditory threshold at a range of frequencies. It appears that 10% or 20% N2O inhalation does not lead to the commonly held view of increased hearing acuity as measured in terms of auditory threshold. Rather, at these levels of N2O inhalation, subjects experience a state similar to a pre-sleep stage, whereby the hearing diminishes but remains active for loud intensity sounds.

The involvement of the styloid process in head and neck pain--a preliminary study

The styloid process and associated structures have been implicated in a variety of craniomandibular dysfunctions and pain complaints. There have been anecdotal reports that treatment directed at this area can result in a dramatic reduction in referred symptoms, somatic pain and autonomic signs as well as an increase in mandibular range of motion. In the past, an elongation of the styloid process was considered necessary for pain and dysfunction symptoms to arise from this area. The patients in this study did not have elongated styloid processes, yet had orofacial pain and dysfunction symptoms seemingly referred from this area. An injection of local anaesthetic and corticosteroid in the area of the styloid process significantly reduced lateral head pain and improved mandibular function in spite of an absence of any demonstrable pathology at the styloid process.

Features of cortically evoked swallowing in the awake primate (Macaca fascicularis)

Although the cerebral cortex has been implicated in the control of swallowing, the output organization of the cortical swallowing representation, and features of cortically evoked swallowing, remain unclear. The present study defined the output features of the primate "cortical swallowing representation" with intracortical microstimulation (ICMS) applied within the lateral sensorimotor cortex. In four hemispheres of two awake monkeys, microelectrode penetrations were made at </=1-mm intervals, initially within the face primary motor cortex (face-MI), and subsequently within the cortical regions immediately rostral, lateral, and caudal to MI. Two ICMS pulse trains [35-ms train, 0.2-ms pulses at 333 Hz, </=30 microA (short train stimulus, T/S); 3- to 4-s train, 0.2-ms pulses at 50 Hz, </=60 microA (continuous stimulus, C/S)] were applied at </=500-micron intervals along each microelectrode penetration to a depth of 8-10 mm, and electromyographic (EMG) activity was recorded simultaneously from various orofacial and laryngeal muscles. Evoked orofacial movements, including swallowing, were verified by EMG analysis, and T/S and C/S movement thresholds were determined. Effects of varying ICMS intensity on swallow-related EMG properties were examined by applying suprathreshold C/S at selected intracortical sites. EMG patterns of swallows evoked from various cortical regions were compared with those of natural swallows recorded as the monkeys swallowed liquid and solid material. Results indicated that swallowing was evoked by C/S at approximately 20% of 1,569 intracortical sites where ICMS elicited an orofacial motor response in both hemispheres of the two monkeys, typically at C/S intensities </=30 microA. In contrast, swallowing was not evoked by T/S in either monkey. Swallowing was evoked from four cortical regions: the ICMS-defined face-MI, the face primary somatosensory cortex (face-SI), the region lateral and anterior to face-MI corresponding to the cortical masticatory area (CMA), and an area >5 mm deep to the cortical surface corresponding to both the white matter underlying the CMA and the frontal operculum; EMG patterns of swallows elicited from these four cortical regions showed some statistically significant differences. Whereas swallowing ONLY was evoked at some sites, particularly within the deep cortical area, swallowing was more frequently evoked together with other orofacial responses including rhythmic jaw movements. Increasing ICMS intensity increased the magnitude, and decreased the latency, of the swallow-related EMG burst in the genioglossus muscle at some sites. These findings suggest that a number of distinct cortical foci may participate in the initiation and modulation of the swallowing synergy as well as in integrating the swallow within the masticatory sequence.

Trajectories of condylar points during nonworking side and protrusive movements of the mandible

STATEMENT OF PROBLEM

During lateral excursive and protrusive jaw movements, condylar points are distant from any instantaneous rotational center. Therefore, it is likely that different condylar points would follow similar trajectories during these movements.

PURPOSE

This study evaluated the effect of changes in condylar point location on trajectories of condylar points on the nonworking side and during a protrusive jaw movement and compared these changes with the effects described for open-close and working-side condylar movements in the same group of subjects.

METHODS

The movements of 5 clinically determined condylar points were recorded in 44 subjects during a contralateral excursion and during protrusion (7 radiographically determined condylar points in 2 subjects).

RESULTS

During any single jaw movement, the trajectory of each condylar point was similar in form and dimension to the other condylar points within that subject.

CONCLUSION

Changes in condylar point location had little effect on the trajectories of condylar points on the nonworking side and during protrusive jaw movement.

Simultaneous recording of mandibular condylar movement and single motor-unit activity at verified sites in the human lateral pterygoid muscle

In recent years, understanding of normal jaw-muscle function has been enhanced by detailed descriptions of their complex internal architecture and of the functional activity of single motor units (SMUs). The lateral pterygoid muscle, however, has been poorly studied, although it is thought to play an important part in the control of jaw and jaw-joint movement. The present study is the first of a series of SMU studies to clarify the normal function of this muscle. The aims were to demonstrate (a) the unequivocal isolation of SMU activity from one or two verified recording sites within the lateral pterygoid, and (b) that these SMUs can be recorded reliably together with condylar movement during simple command jaw movements. Recordings of SMU activity were made with fine-wire electrodes from sites within the superior and inferior heads of the right lateral pterygoid during biting or command lateral jaw movements and combined with recordings of condylar and mid-incisor point movement. Recording sites were verified by computed tomography. In four young adults, the activities of 17 SMUs were reliably discriminated at seven recording sites within the lateral pterygoid. The units could be recorded during repeated trials of the same movement throughout a recording session with no appreciable change in amplitude or waveform. Units could also be discriminated simultaneously at separate recording sites--one in the superior head and the other in the inferior head. These data demonstrate that SMU activity can be recorded from verified sites within the lateral pterygoid simultaneously with condylar movement during command jaw movements.

Electromyographic evidence for functional heterogeneity in the inferior head of the human lateral pterygoid muscle: a preliminary multi-unit study

OBJECTIVE

Functional heterogeneity, i.e. regional or selective activation of subpopulations of fibres within a muscle, has been described in some jaw and limb muscles. Each head of the lateral pterygoid muscle may also be functionally heterogeneous. The aims of this investigation were to develop a technique to test this hypothesis, and to use this technique to determine whether there is any multi-unit electromyographic (EMG) evidence for functional heterogeneity within the inferior head of the lateral pterygoid (IHLP).

METHODS

In 3 human subjects without craniomandibular disorders, recordings were made of condylar movement and multi-unit EMG activity from two sites in the IHLP during repeated trials of a contralateral (n = 21) and a protrusive (n = 26) jaw movement. The recording sites within IHLP were approached extraorally (labelled IHLP-extra) and were verified by computer tomography (CT); the other (IHLP-intra) were from sites in IHLP approached intraorally.

RESULTS

In each subject, the time of occurrence of the peak filtered signal from IHLP-extra was significantly different (P<0.05) from IHLP-intra for all protrusion trials but not for contralateral trials.

CONCLUSIONS

The data suggest a task-dependent change in motor unit recruitment order within IHLP and that IHLP is functionally heterogeneous.

Organization of somatosensory areas I and II in marsupial cerebral cortex: parallel processing in the possum sensory cortex

Organization of somatosensory areas I and II in marsupial cerebral cortex: parallel processing in the possum sensory cortex. Controversy exists over the organization of mammalian thalamocortical somatosensory networks. An issue of particular contention is whether the primary and secondary somatosensory areas of cortex (SI and SII) are organized in a parallel or serial scheme for processing tactile information. The current experiments were conducted in the anesthetized brush-tail possum (Trichosurus vulpecula) to determine which organizational scheme operates in marsupials, which have taken a quite different evolutionary path from the placental species studied in this respect. The effect of rapid reversible inactivation of SI, achieved by localized cortical cooling, was examined on both evoked potential and single neuron responses in SII. SI inactivation was without effect on the amplitude, latency, and time course of SII-evoked potentials, indicating that the transient inputs responsible for the SII-evoked potential reach SII directly from the thalamus rather than traversing an indirect serial route via SI. Tactile responsiveness was examined quantitatively before, during, and after SI inactivation in 16 SII neurons. Fourteen were unchanged in their responsiveness, and two showed some reduction, an effect probably attributable to the loss of a facilitatory influence exerted by SI on a small proportion of SII neurons. The temporal precision and pattern of SII responses to dynamic forms of mechanical stimuli were unaffected, and temporal dispersion in the SII response bursts was unchanged in association with SI inactivation. In conclusion, the results establish that, within this marsupial species, tactile inputs can reach SII directly from the thalamus and are not dependent on a serially organized path through SI. A predominantly parallel organizational scheme for SI and SII operates in this representative of the marsupial order, as it does in a range of placental mammals including the cat and rabbit, the tree shrew and prosimian galago, and at least one primate representative, the marmoset monkey.

Trajectories of condylar points during working-side excursive movements of the mandible

STATEMENT OF PROBLEM

Trajectories of different condylar points provide different interpretations of condylar movement during open-close jaw movements. Movement of the working-side condyle is often assessed clinically by recording the trajectory of a single arbitrary condylar point.

PURPOSE

This study examined the effect of the differences in condylar point location on condylar point movement trajectories during a working-side movement.

METHODS

Different points exhibited different trajectories during a single working-side movement in each of 44 subjects.

RESULTS

Up to 40% of a point's displacement could be attributed simply to the location of the point.

CONCLUSIONS

Interpretation of condylar movement on the working side within a subject depends on the point chosen.

Electromyographic activity of the human lateral pterygoid muscle during contralateral and protrusive jaw movements

Understanding of the normal function of the lateral pterygoid muscle is limited. The principal aim here was to determine whether there is a progressive increase in lateral pterygoid activity as the mandibular condyle moves downwards and forwards as would be expected if the muscle is concerned with the precise horizontal positioning of the mandible. In eight humans, recordings were made of the activity of the superior (SHLP) and inferior (IHLP) heads of the lateral pterygoid and the masseter, anterior temporal, posterior temporal and digastric muscles, together with the movement of the palpated lateral condylar pole (JAWS-3D tracking system) during trials of a contralateral and a protrusive jaw movement. Recording sites in SHLP and, in one participant, IHLP were verified by computed tomography. In each participant there was a progressive increase in the rectified and smoothed SHLP and IHLP activity in association with condylar movement during the contralateral and protrusive jaw movement. Further, irregularities in condylar movement, which reflected variations in the rate at which the jaw was moved, were correlated in time with prominent bursts of SHLP and IHLP activity. In all participants there was a consistently high correlation coefficient between the rectified and smoothed SHLP and IHLP activity and condylar displacement during the contralateral or protrusive jaw movements. For example, the mean (+/-SD) correlation between anterior condylar translation during contralateral excursion and SHLP activity was 0.91+/-0.09, and for IHLP 0.96+/-0.02. For the masseter, anterior temporal, posterior temporal and digastric muscles, mean r-values were, respectively, 0.10+/-0.77; -0.14+/-0.72; 0.24+/-0.78; 0.54+/-0.47. When treated as a group the correlation coefficients for SHLP and IHLP were statistically significantly different from the correlation coefficients for the other muscles treated as a group (ANOVA; p < 0.002 for correlation with anterior translation). These observations support the notion that the lateral pterygoid provides the principal driving force for moving the jaw forwards or laterally in protrusive or lateral excursive condylar movements. Further, the data suggest that the muscle plays a part in the fine control of jaw movements.

Polymer-based lanthanide luminescent sensor for detection of the hydrolysis product of the nerve agent Soman in water

The techniques of molecular imprinting and sensitized lanthanide luminescence have been combined to create the basis for a sensor that can selectively measure the hydrolysis product of the nerve agent Soman in water. The sensor functions by selectively and reversibly binding the phosphonate hydrolysis product of this agent to a functionality-imprinted copolymer possessing a coordinatively bound luminescent lanthanide ion, Eu3+. Instrumental support for this device is designed to monitor the appearance of a narrow luminescence band in the 610-nm region of the Eu3+ spectrum that results when the analyte is coordinated to the copolymer. The ligand field shifted luminescence was excited using 1 mW of the 465.8-nm line of an argon ion laser and monitored via an optical fiber using a miniature spectrometer. For this configuration, the limit of detection for the hydrolysis product is 7 parts per trillion (ppt) in solution with a linear range from 10 ppt to 10 ppm. Chemical and spectroscopic selectivities have been combined to reduce the likelihood of false positive analyses. Chemically analogous organophosphorus pesticides tested against the sensor have been shown to not interfere with determination.

The in vitro inhibition of Phytophthora clandestina by some rhizobia and the possible role of Rhizobium trifolii in biological control of Phytophthora root rot of subterranean clover

The interaction between 29 isolates of Rhizobium and the in vitro growth of 3 strains of Phytophthora clandestina was investigated to determine the potential of these bacteria as biological control agents against root rot of subterranean clover (Trifolium subterraneum L.). The biological control activity of Rhizobium on the severity of root disease in seedlings was also investigated under glasshouse conditions. Thirteen of the 29 Rhizobium isolates caused significant reductions in the hyphal growth of the 3 P. clandestina isolates examined. Inoculation of seedlings with Rhizobium trifolii reduced the severity of root disease by 14–58% with corresponding increases in dry matter production of 20–73%. These results indicate that Rhizobium species have potential as biological control agents against the root rot of T. subterraneum seedlings caused by P. clandestina.