Biomedical subjects

Peter Myers

Publications and source records attributed to Peter Myers.

5 recordsLinked to original sources

PubMed2006

Real-time image acquisition for absorbance detection and quantification in thin-layer chromatography.

This paper presents the first quantitative study of real-time acquisition of images of spots on thin-layer chromatographic plates during development. Procedures are described for imaging using a CCD camera and for image processing, incorporating corrections for fixed pattern effects and compensation for the moving solvent front, to measure the absorbance of the analyte. Imaging of Sudan II was carried out in transmission mode, and peak areas were found to be time-independent. Quantification of the relationship between peak area and sample loading was established over the range 1-50 ng. After averaging 55 images obtained during a single chromatographic run, which attenuates noise contributions from local nonuniformities in the sorbent layer, precision and detection limits were found to be comparable with values obtained in previous work using offline measurements.

Azo Compounds↗

PubMed2005

Quantitative measurements on wetted thin layer chromatography plates using a charge coupled device camera.

This paper presents the first study of imaging of spots on thin-layer chromatographic plates whilst still wet with solvent. Imaging and quantification of Sudan II after development with dichloromethane was carried out in both reflectance and transmission modes, using a charge coupled device (CCD) camera. The relationship between peak area and sample loading was established at low sample loading, and found to be linear over an order of magnitude for both wet and dry modes with r2-values > 0.99. All data processing was carried out using the Beer-Lambert equation. Curvature at high loadings in the plots of integrated absorbance as a function of sample loading was accounted for using an empirical expression designed for use with the Kubelka-Munk treatment and apparent absorbance of the stationary phase due to scattering. Results are consistent with an effective pathlength significantly longer than the thickness of the sorbent layer. The limit of detection on a dry plate (0.5 ng) was found to be lower than on a wetted plate (2 ng). Precision was found to be 1-4% RSD intra-plate and 8-14% RSD inter-plate. Results are compared with quantification of the same analyte on dried plates.

Azo Compounds↗

PubMed2005

Timing of rotator cuff activation during shoulder external rotation in throwers with and without symptoms of pain.

STUDY DESIGN: Fine-wire EMG rotator cuff onset time analysis in 2 matched groups of throwers with and without pain. OBJECTIVE: To identify if there is a difference in the activation patterns of the rotator cuff muscles during a rapid shoulder external rotation task between throwers with and without pain. BACKGROUND: The coordinated action of the rotator cuff is recognized as essential for glenohumeral joint control in the throwing athlete. Identification of abnormalities occurring in muscle activation patterns for injured athletes is relevant when prescribing rehabilitative exercises. METHODS AND MEASURES: Twelve throwers with shoulder pain were compared to a matched group of 11 asymptomatic throwers. Participants were matched for age, height, body mass, and habitual activity. Fine-wire EMG electrodes were inserted into the subscapularis, supraspinatus, and infraspinatus. EMG activity was measured during a reaction time task of rapid shoulder external rotation in a seated position. The timing of onset of EMG activity was analyzed in relation to visualization of a light (reaction time) and to the onset of infraspinatus activity (relative latency). RESULTS: In the group with shoulder pain, the onset of subscapularis activity was found to be significantly delayed (reaction time, P = .0018; relative latency, P = .0005) from the onset of infraspinatus activity when compared to the control group. CONCLUSIONS: The presence of shoulder pain in these athletes was associated with a difference in the onset of subscapularis EMG activity during a rapid shoulder external rotation movement. This was an initial step in the understanding of the joint protection mechanisms of the glenohumeral joint and the problems that occur in throwers. This information may assist in providing future guidelines for more effective rehabilitation and prevention strategies for this condition.

Adult↗

PubMed2004

Development and assessment of a miniaturised centrifugal chromatograph for reversed-phase separations in micro-channels.

This paper describes the micro-fabrication and preliminary assessment of a miniature polydimethylsiloxane (PDMS) device for performing rapid, parallel liquid phase chromatographic separations driven by centrifugal force in microchannels. Device components include a main separating channel, into which a high performance liquid chromatography (HPLC) particulate stationary phase was packed under pressure by application of centrifugal force, in addition to solvent and sample reservoirs. Also described are methods for sealing such devices based upon partial polymerisation of PDMS. The mobile phase flow rate through a typical device was measured and several important chromatographic parameters determined from a test separation. An expression describing mobile phase flow through packed channels was also developed, based upon work on liquid flow in open micro-channels. Good agreement between predicted and measured flow rates were observed. Some predictions for potential uses of such devices and possibilities for further miniaturisation are discussed.

Journal Article↗

PubMed2003

Is bone tunnel osseointegration in hamstring tendon autograft anterior cruciate ligament reconstruction important?

A 27-year-old man underwent anterior cruciate ligament (ACL) reconstruction using 4-strand hamstring autograft with femoral and tibial interference screw fixation. Four weeks after surgery, he developed a discharging hematoma through the graft harvest-tibial tunnel incision, which persisted. The patient required further surgical intervention 7 weeks after the initial surgery. The wound was debrided, the tibial interference screw was removed, and the tibial tunnel was completely cleared of graft remnants. Arthroscopy of the knee was performed, in which the ACL graft appeared healthy and viable. No evidence of intra-articular sepsis was found. Postoperatively, the rehabilitation program was uneventful and, at 36 months, the patient has unrestricted activity and no clinical evidence of excessive ACL laxity. This case supports the importance of marginal articular surface healing of the ACL graft, suggesting that tibial intratunnel healing becomes redundant.

Adult↗