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Biomedical subjects

J G Anson

Publications and source records attributed to J G Anson.

At least 19 recordsLinked to original sources
PubMed2002

EMG discharge patterns during human grip movement are task-dependent and not modulated by muscle contraction modes: a transcranial magnetic stimulation (TMS) study.

Our previous study revealed that, during tonic muscle contraction, remarkable functional differences among intrinsic and extrinsic muscles were observed during two different grip movements, i.e., precision and power grips. To verify whether this evidence is true even under the phasic muscle contraction, magnetic stimulation was delivered over the left scalp while a normal human subject performed phasic precision or power grip responses of the right-hand fingers in a simple reaction time (SRT) paradigm. Magnetic stimulation delivered during the latent period revealed different cortico-motoneuronal excitations between the two grip responses. In particular, the contributions of extensor carpi radialis (ECR) muscle were definitely different between the two grip responses, although motor-evoked potentials (MEPs) of first dorsal interosseous (FDI) prior to, and after EMG onset of movement initiation, were not different. These results were similar to previous results obtained during tonic muscle contraction. Thus, we have concluded that the task-dependent EMG discharge pattern in finger manipulation could not be modulated by muscle contraction modes.

Action Potentials↗
PubMed2001

Interactions among end-effectors and movement parameters influence reaction time in discrete, rapid aimed movements.

Two reliable findings in discrete, rapid aimed movements are that reaction time increases with decrease in target diameter (for the short-length movements), and reaction time is not affected by movement length [Journal of Experimental Psychology, Human Perception and Performance 104 (2) (1975) 147]. Participants normally use a short stylus (SS) to tap targets located on either side of a central (aligned with body midline) start-point with no restrictions imposed on the initial posture of the limb or segmental recruitment except as determined by movement conditions. Thus, the effects of movement parameters on reaction time in previous work are potentially confounded with the effect of initial posture of the limb at the start-point, along with order and amount of the contribution of segments recruited in response execution. Two experiments were performed to resolve the confounding between initial posture and recruitment of limb segments. In the first experiment a conventional stylus (pen-like) was employed and the starting position of the limb was aligned either with the body midline or with the participant's right shoulder. The effect of starting position on reaction time was not significant. In the second experiment the starting position was in line with the right shoulder. Two groups participated. One group used a conventional stylus. For the second group a modified (lengthened) stylus was used that permitted initial limb posture and number of limb segments recruited to be held constant across an extended range of movement lengths. When similar sets of limb segments were used, reaction time increased with decreasing movement length and diminishing target diameter. These findings suggest that uncontrolled initial limb posture, uncontrolled order of joint(s) recruitment, and the subsequent inclusion of reaction time values from incompatible sources may, in the final analysis, have confounded previous work investigating movement amplitude and target diameter effects on reaction time.

Adult↗
PubMed2000

Parameter precuing and motor preparation.

A movement task was used to investigate the effects of precued variables on reaction time. The task involved rapid rotation of a hand-held manipulandum to target locations and required either pronation or supination of the forearm through short or long extent. The effects on reaction time of precues signalling target direction, extent, or a combination of direction and extent, were measured. The longest reaction times occurred when no information about direction or extent was provided in the precue (all parameters uncertain). Complete prior specification of target position produced the shortest reaction times. Specification of direction when extent was uncertain produced a significantly larger reduction in reaction time than specification of extent when direction was uncertain. Prior specification of extent also produced a small but significant reduction in reaction time relative to the condition in which direction and extent were specified in a mutually conditional manner. The results are discussed in relation to parameter precuing and motor programming, in which the direction is programmed by the pre-selection of neurons representing the muscles to be used in the task while programming of extent is represented by their level of activity during task performance.

Acoustic Stimulation↗
PubMed1999

Natural goal-directed movements and the triphasic EMG.

Triphasic electromyographic (EMG) patterns have been described as characteristic of rapid, discrete, uniplanar, goal-directed movements. This experiment examined the effects of Response Type (experimenter- vs. subject-determined), Hand (preferred vs. nonpreferred), and Practice (early vs. late) on performance accuracy, and specific temporal EMG and kinematic measures during a dart throw. EMG was recorded from triceps (main agonist), brachioradialis, and biceps (main antagonist). The number of trials in which a triphasic EMG occurred varied systematically across conditions. The experimenter-determined, early practice condition resulted in greatest frequency (92%) of trials displaying a triphasic EMG and least accurate performance. In contrast, the lowest frequency (79%) of triphasic EMG and most accurate performance occurred in the subject-determined, late practice condition. The association among 14 temporal EMG, and kinematic measures for each trial of the dart throw was analyzed with multivariate factorial ANOVA. Four clusters of variables emerged: initial phase, braking phase, terminal phase, and movement speed and duration. Variables contributing to the initial-phase cluster were most strongly associated within the experimenter-determined, early practice condition, and the strength of association was directly related to diminished performance accuracy. Paradoxically, best performance accuracy (subject-determined, late practice) was identified with a weaker association among variables representing the initial phase.

Adult↗
PubMed1998

Foreperiod length, but not memory, affects human reaction time in a precued, delayed response.

The effect of foreperiod length on reaction time in memorized (MM) and nonmemorized (NM), precued, delayed responses was investigated. Six subjects participated in one long and one short foreperiod schedule testing session. An aiming task, using elbow supination/pronation, in response to a visual stimulus was employed. In the MM condition, target spatial information was available for a fraction of the foreperiod duration. In the NM condition, target information was available continuously until the subject attained the target position. Subjects responded with a significantly longer latency in the long foreperiod schedule. Within each foreperiod schedule, the shortest foreperiod resulted in significantly longer reaction time. However, the absolute value of foreperiod did not have a major effect on reaction time latency. Memorization and nonmemorization conditions did not affect reaction time.

Adult↗
PubMed1998

Does having to remember the position of a target improve reaction time?

In the monkey, reaction time in a precued delayed response task was found to be faster when the animals had to remember the precue than when it was continually available (Smyrnis, Taira, Ashe, & Georgopoulos, 1992). We investigated whether this reflects a general principle that applies to all types of precued tasks. However, we found the opposite result in a simpler task in humans. Our findings suggest that the beneficial effect of a memory requirement on reaction time in the monkey may reflect an effect of task difficulty, rather than a fundamental process involved in all precued movement tasks.

Adult↗
PubMed1997

A homogeneous method to quantify mRNA levels: a hybridization of RNase protection and scintillation proximity assay technologies.

A novel method to measure mRNA levels has been developed by combining the detection capabilities of RNase protection (RPA) with the quantification advantages of scintillation proximity assay (SPA) technology. Sample processing is reduced to the addition of a single reagent post RNase digestion. As a model system, the inducible expression of rat apolipoprotein-A1 mRNA has been measured by both traditional gel-based RPAs and the SPA-based RPA assay. Results demonstrate that the ribonuclease protection proximity assay (RiPPA) faithfully reproduces the gel-based results and is at least as sensitive as many existing methods.

Animals↗
PubMed1997

Quantification of hepatitis B virus DNA using competitive PCR and a scintillation proximity assay.

A rapid assay for the quantification of hepatitis B virus DNA in human serum was developed. The principle of the method combines competitive polymerase chain reaction (cPCR) (for the controlled amplification of hepatitis B virus DNA) and scintillation proximity assay (SPA) technology (for rapid detection and quantitation of PCR products). It also incorporates a reproducible and simple method for the preparation of serum DNA suitable for PCR amplification. The assay has a better linear dynamic range than traditional methods that use 32P to detect PCR products. It was applied to a range of hepatitis B virus (HBV) surface antigen positive (HBsAg + ) sera, and shown to be more sensitive than a commercially available HBV DNA kit.

DNA, Viral↗
PubMed1997

High-throughput RT-PCR analysis of multiple transcripts using a microplate RNA isolation procedure.

We have developed a high-throughput, multiplex reverse transcription PCR (RTPCR) assay that is suitable for the analysis of medium-to low-copy cellular RNA transcripts from small numbers of cells (10(4)). High throughput was attained by utilizing microplate-based RNA extraction and RTPCR protocols, followed by PCR product visualization of a multiwelled agarose gel, stained with SYBR Green I dye. The transcriptional assay was unaffected by solvents (dimethyl sulfoxide and methanol) routinely used in high-throughput drug screens at concentrations required for compound solubilization. Furthermore, it has been used successfully for the investigation of differential mRNA expression levels of tumor necrosis factor alpha (TNF-alpha) and Interleukin-1 beta (IL-1 beta) in lipopolysaccharide (LPS)-stimulated THP-1 cells (a human monocytic cell line) and the identification of specific IL-1 beta transcriptional inhibitors.

Benzothiazoles↗
PubMed1996

Development of a high-volume in situ mRNA hybridization assay for the quantification of gene expression utilizing scintillating microplates.

A high-volume plate-based in situ hybridization assay has been developed, utilizing Amersham Cytostar-T scintillating microplates. This assay reliably detects specific mRNA transcripts at the level of 10-20 copies per cell. Radiolabeled antisense riboprobes specific for c-fos and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as well as nonhomologous vector-derived control probes were used to compare mRNA levels in quiesced rat A10 smooth muscle cells after stimulation with platelet-derived growth factor (PDGF). Maximal c-fos induction occurred following stimulation of A10 cells with 30 ng/ml of PDGF, corresponding to a signal from the c-fos probe of 700 cpm. The nonhomologous control background of 50 cpm and the GAPDH signals of 1700 cpm were independent of stimulation with PDGF or serum. Using PDGF, at 30 ng/ml, quiesced cells were stimulated at various times to provide an induction time course for c-fos mRNA which peaked at 30 min and returned to basal levels within 2 h. Comparison with parallel Northern blotting experiments showed this in situ assay to be at least 20-fold more sensitive and much more rapid to perform.

Animals↗
PubMed1995

Evidence for soleus H-reflex depression induced by ballistic head rotation.

In this study, we described a sequence of changes of the electromyographic (EMG) and depression of the soleus (Sol) H-reflex that precede and follow the onset of ballistic head rotation in freely standing human subjects. During head rotation, a sequence of EMG changes occurred simultaneously in Sol and in biceps femoris muscle (BF). Specifically, changes to Sol EMG included deactivations (EMG silent period) and H-reflex depression coincident with BF excitation. Thus, in the case of ballistic head movement, control commands for anticipatory postural adjustment appear to excite BF and inhibit Sol in a similar way to that previously described for the onset of arm movement.

Adult↗
PubMed1994

High-level expression of the phenylalanine ammonia lyase-encoding gene from Rhodosporidium toruloides in Saccharomyces cerevisiae and Escherichia coli using a bifunctional expression system.

A chimeric yeast promoter (pPGK::REP2), capable of directing high-level gene expression in both Saccharomyces cerevisiae and Escherichia coli, has been constructed. It was derived by fusing the promoter of the yeast PGK gene (encoding phosphoglycerate kinase) to a region residing immediately 5' to the yeast 2 mu plasmid REP2 gene (encoding a trans-acting plasmid maintenance protein). In S. cerevisiae, transcripts initiated within the REP2-derived moiety of the promoter, but the transcription start point was dictated by the PGK determinator sequence. Promoter function in E. coli was due to the presence of consensus prokaryotic -35 and -10 motifs in the REP2 moiety. To facilitate expression studies, the promoter was incorporated into a versatile series of S. cerevisiae/E. coli shuttle vectors which provided a choice of selectable marker and copy number in S. cerevisiae. To maximise translational efficiency, a novel cloning strategy was devised which allows the juxtaposition of genes to the promoter such that the heterologous AUG replaces that of the REP2 AUG, without any alteration in the surrounding nucleotide (nt) context. This strategy was used to place both the Tn903 neo gene and the Rhodosporidium toruloides phenylalanine ammonia lyase (PAL)-encoding gene under the transcriptional control of pPGK::REP2. In the former case, cells became resistant to extremely high levels of Geneticin (> 3 mg/ml in the case of S. cerevisiae). In the case of the latter, PAL was shown to accumulate to approx. 9 and 10% of total soluble protein in S. cerevisiae and E. coli, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1991

The cost benefit of rehabilitation of injured workers in New Zealand.

A multidisciplinary rehabilitation centre was established to address the needs of people with mild to moderate disability who had not worked for prolonged periods of time. A fitness based programme assisted 10 of the 20 who had been off work for more than six months to return to activity. Six and eighteen month follow up confirmed the durability of placement of most workers who had returned to work, and that projected benefits were achieved. Benefits were defined as savings in earnings related compensation (ERC), and compared to the costs of establishing and running the centre. Sensitivity analysis ascribing between 100% and 50% of benefit to the programme showed a positive benefit cost ratio, with benefits discounted at a rate of 10% over 10 years. With 75% ascribed, the project produced benefit cost ratio of about 1.5:1 in the first year, 2.8:1 in the second year, and rising to 6.2:1 in the fifth year and 10:1 by the tenth year. With only 50% ascribed, the benefit over the same times was 1.0:1, 1.9:1, 4.1:1 and 6.7:1 by the tenth year. These calculations probably underestimate true benefits.

Adult↗
PubMed1990

The rehabilitation of injured workers in New Zealand: a pilot study.

At the request of the local office of the Accident Compensation Corporation (ACC) we established a centre which offered a multidisciplinary rehabilitation programme consisting of a full assessment and an eight week individually planned and monitored fitness programme. The clients progressed to occupational therapy, work trials, and later to paid work. The programme included education about back care and health maintenance, and relaxation techniques. Of the 48 injured people who attended the centre, 37 were assessed as suitable to enter the programme, and 32 people took part. Outcome, measured as return to work or change in assessed fitness to work, was not related to age, sex, marital status, length of time since accident, or work category. Only 25% of workers returned to jobs in medium or heavy manual work. Sickness impact profile total and physical scores improved over the programme, but did not correlate significantly with return to work or fitness for work. Client perception of benefit was not significantly related to outcome. We analysed data from the 20 clients with claims longer than 6 months separately because matched case controls could not be provided by the ACC. Six months after completion of the programme, four were in paid employment, four in prolonged work trials, one in a job partly paid by the ACC, and one setting up his own business. Their return to the work force demonstrated the effectiveness of the centre in restoring people to function after prolonged periods of inactivity.

Accidents, Occupational↗
PubMed1989

Effects of moment of inertia on simple reaction time.

Two experiments examined the effect of altering the moment of inertia within an anatomical unit on simple reaction time (SRT), premotor time (PMT), and motor time (MOT) during the initiation of a discrete rapid movement. In Experiment 1 (N = 14), moment of inertia of the forearm was increased with the addition of a weighted cuff fastened around the wrist. In Experiment 2 (N = 7), moment of inertia was altered by the addition of a weighted sleeve to the index finger prior to rapid extension of the digit. Results from both experiments were unequivocal. An increase in the moment of inertia resulted in a significant increase in SRT and MOT but had no significant effect on PMT. Within selected anatomical unites (forearm and index finger), an increase in the moment of inertia does not appear to require additional neuromotor programming time but does influence the overall duration of response initiation.

Journal Article↗
PubMed1987

Complete nucleotide sequence of the Rhodosporidium toruloides gene coding for phenylalanine ammonia-lyase.

The complete nucleotide sequence of the Rhodosporidium toruloides gene coding for the enzyme phenylalanine ammonia-lyase (PAL) has been determined. The primary structure of PAL was deduced from the nucleotide sequence of the two cDNA clones, pPAL1 and pPAL2, which covered the entire amino acid-coding sequence. Comparison of cDNA and genomic sequences of pal revealed the presence of six introns. The nucleotide sequences of these introns were compared to those from other fungi. The primary amino acid sequence of the enzyme exhibits only 30.8% identity with the determined primary sequence of PAL from Phaseolus vulgaris. Upstream from the structural gene there is a stretch of C + T-rich DNA similar to that found upstream from a number of Neurospora and Saccharomyces cerevisiae genes. In the case of S. cerevisiae, these C + T-rich sequences are thought to be involved in the transcription of highly expressed genes.

Amino Acid Sequence↗
PubMed1986

Interaction between visually and kinesthetically triggered voluntary responses.

A voluntary motor response that is prepared in advance of a stimulus may be triggered by any sensory input. This study investigated the combination of visual and kinesthetic inputs in triggering voluntary torque responses. When a visual stimulus was presented alone, subjects produced a fast and accurate increase in elbow flexion torque. When a kinesthetic stimulus was presented instead of the visual stimulus, subjects produced a similar response with a reduced response latency. When a visual stimulus was presented in combination with a kinesthetic stimulus, subjects initiated their responses after either a visual or a kinesthetic response latency, depending on the relative timing of the two stimuli. An analysis of response amplitude suggested that when visual and kinesthetic stimuli were combined, both stimuli triggered a response. The results are more consistent with a simple behavioral model of addition of visual and kinesthetic responses (which predicts that the response to combined stimuli should be the sum of individual responses) than with a model of exclusion of one response (which predicts that the response to combined stimuli should be identical to either the visual or the kinesthetic response). Because addition of visually and kinesthetically triggered responses produced a response with an erroneously large amplitude, it is suggested that visual and kinesthetic inputs are not always efficiently integrated.

Journal Article↗