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Biomedical subjects

R J Neal

Publications and source records attributed to R J Neal.

11 recordsLinked to original sources
PubMed1995

Self-selected manual lifting technique: functional consequences of the interjoint coordination.

The pattern of movement self-selected by 39 subjects to lift light loads from 9 cm above the ground is described in kinematic and electromyographic terms. Hamstring length changes were estimated from hip and knee angular kinematics. Subjects adopted a posture at the start of the lift intermediate between stoop and full-squat postures. A consistent coordination between knee, hip, and lumbar vertebral joints during lifting was described through calculation of the relative phase between adjacent joints and found to be exaggerated with increases in load mass. During the early phase of lifting, knee extension leads hip extension, which in turn leads extension of the lumbar vertebral joints. Early in the lifting movement, when load acceleration is greatest, the erectores spinae are thus relatively long and shortening slowly. Both of these factors produce greater back extensor strength. Rapid hamstring shortening is also delayed, which enhances their strength, and coactivation of the monoarticular knee extensors and biarticular hamstring observed early in the lifting movement suggested that the knee extensors contribute to hip extension through a tendinous action of the hamstrings.

Adult↗
PubMed1993

Relative phase quantifies interjoint coordination.

This note illustrates by example how expression of joint movement on a phase plane can quantitatively describe multijoint coordination during complex actions. Automatic digitisation of high-speed video records was used to obtain lumbar vertebral, hip, knee and ankle joint angular kinematics in the sagittal plane of a subject performing a symmetric two-handed lifting movement. A consistent proximal-to-distal coordination was illustrated via angle-angle and relative phase angle presentations. During bending to pick up a load, the joints began their movement in the order proximal to distal while the reverse order of joint involvement occurred during extension. Phase angle relationships between joints may provide sufficiently sensitive measurements to identify changes in multijoint coordination induced by alterations in task variables such as (in the case of lifting) object mass, lifting height and load moment. Information regarding multijoint coordination is likely to be important in attempting to understand the respective roles and interaction between the bi and monarticular muscles which are involved in everyday complex actions like lifting.

Adult↗
PubMed1992

Against relative timing invariance in movement kinematics.

The kinematics of stair climbing were examined to test the assertion that relative timing is an invariant feature of human gait. Six male and four female subjects were video-recorded (at 60 Hz) while they climbed a flight of stairs 10 times at each of three speeds. Each gait cycle was divided into three segments by the maximum and minimum angular displacement of the left knee and left foot contact. Gentner's (1987) analysis methods were applied to the individual subject data to determine whether the duration of the segments remained a fixed proportion of gait cycle duration across changes in stair-climbing speed. A similar analysis was performed using knee velocity maxima to partition the gait cycle. Regardless of how the gait cycle was divided, relative timing was not found to remain strictly invariant across changes in speed. This conclusion is contrary to previous studies of relative timing that involved less conservative analysis but is consistent with the wider gait literature. Strict invariant relative timing may not be a fundamental feature of movement kinematics.

Adult↗
PubMed1991

Bidirectional promoter and terminator regions bracket mmr, a resistance gene embedded in the Streptomyces coelicolor A3(2) gene cluster encoding methylenomycin production.

Low- and high-resolution nuclease mapping of in vivo transcripts, and in vitro transcription reactions using purified RNA polymerase, were used to analyse transcription of and around the mmr gene, which specifies resistance of Streptomyces coelicolor A3(2) to methylenomycin (Mm) and is located in the middle of a cluster of Mm-production-encoding genes. Transcription of mmr is from a single major start point (tsp) which is separated by only 81 bp from a divergent tsp. A pattern of direct and inverted repeats in the nucleotide sequence in this region may play a part in regulation of these promoters. The 3' end of the mmr transcript overlaps by 20-30 bp the 3' end of an RNA molecule involved in Mm production. The converging transcripts both terminate at the same large inverted repeat in the DNA. Purified RNA polymerase terminated transcription at this sequence in vitro (albeit only in one orientation).

Anti-Bacterial Agents↗
PubMed1988

The gait of pacers. 1: kinematics of the racing stride.

Standardbred pacers have been studied under race conditions to describe the gait of the pacer, and to determine relationships between stage of the race, finish order and selected gait kinematics. Overlap increased with the stage of the race while pacing speed decreased marginally for low order pacers and increased for high order finishers. High order finishing pacers appear to have greater stance and stride lengths than do low order finishers. Pacers could be separated into low order and high order groups on the basis of their movement patterns. High order pacers exhibited greater ranges of limb motion than did low order finishers.

Animals↗
PubMed1988

The gait of pacers. 2: factors influencing pacing speed.

Standardbred pacers were studied at four different nominated speeds and selected gait kinematics were analysed to determine factors which contribute to pacing speed. A deterministic model is proposed in which pacing speed is a function of stride length and stride timing variables. Stance length and suspension time remained relatively constant over the different pacing speeds. Variables which discriminated best between pacing speeds were suspension length and overlap time. At near maximal speed, the pacers increased speeds with increased stride length. This was attributed to an increased suspension length with little difference in suspension times. A 22 per cent increase in pacing speed resulted in a 13 per cent increase in stride length, 26 per cent increase in suspension distance, 8 per cent increase in stride frequency, 35 per cent and 16 per cent increases in advanced placement and completion times and a 23 per cent decrease in the period of overlap.

Animals↗
PubMed1987

Nucleotide sequence analysis reveals similarities between proteins determining methylenomycin A resistance in Streptomyces and tetracycline resistance in eubacteria.

Previous studies had localised the gene (mmr) for resistance to methylenomycin A (Mm) to a 2.5-kb PstI fragment in the middle of a cluster of Mm biosynthetic genes from the Streptomyces coelicolor plasmid SCP1. In this paper, the gene has been more precisely located by sub-cloning, and the nucleotide sequence of the whole fragment has been determined. The predicted mmr-specified protein (Mr 49238) would be hydrophobic, with some homology at the amino acid level to tetracycline-resistance proteins from both Gram-positive and Gram-negative bacteria. Comparisons of hydropathy plots of the amino acid sequences reinforces the idea that the proteins are similar. It is suggested that Mm resistance may be conferred by a membrane protein, perhaps controlling efflux of the antibiotic. No significant homology was detected by hybridisation analysis between mmr and a cloned oxytetracycline (OTc)-resistance gene (tetB) of the OTc producer Streptomyces rimosus, and no cross-resistance was conferred by these genes. Sequences on both sides of mmr appear to encode proteins. The direction of translation in each case would be opposite to that of mmr translation. This suggests that mmr is transcribed as a monocistronic mRNA from a bidirectional promoter. An extensive inverted repeat sequence between the stop codons of mmr and the converging gene may function as a bidirectional transcription terminator.

Amino Acid Sequence↗
PubMed1985

Scaling segmental moments of inertia for individual subjects.

The purpose of this investigation was to validate methods of scaling human segmental moments of inertia for the transverse principal axis. Firstly, two methods of scaling Chandler et al.'s (Pamphlets DOT HS-801 430 and AMRL TR-74-137, Wright Patterson Air Force Base, OH, 1975) mean subject data to estimate the segmental moments of inertia were used. Chandler et al.'s data were scaled using body mass and segment length (formula 1) or body mass and standing height (formula 2). These data were then compared with a procedure of using the cadaver whose anthropometric measurements most closely match those of the subject. The difference between the criterion data (Chandler's subject data) and scaled values were plotted on scatter diagrams with confidence limits of p less than 0.05 at d.f. = 17. For procedure 1, 43% of the scaled values were plotted within the confidence limits using formula (2) (mass and standing height), compared with 26% for formula (1) (mass and segment length). Formula (1) markedly underestimated the tallest and heaviest subjects. In procedure 2, only 16% and 21% of the scaled values, using formula (1) and (2), respectively, fell within the confidence limits. Results suggested that scaling formulae approximate the moment of inertia of body segments with only limited accuracy. However, if scaling was to be adopted then mean moment of inertia data from an appropriate data set, using the formula that incorporates subject mass and standing height, gave results closest to the criterion value.

Anthropometry↗