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Biomedical subjects

J S Stephens

Publications and source records attributed to J S Stephens.

8 recordsLinked to original sources

Perfusion flow bioreactor for 3D in situ imaging: investigating cell/biomaterials interactions.

The capability to image real time cell/material interactions in a three-dimensional (3D) culture environment will aid in the advancement of tissue engineering. This paper describes a perfusion flow bioreactor designed to hold tissue engineering scaffolds and allow for in situ imaging using an upright microscope. The bioreactor can hold a scaffold of desirable thickness for implantation (>2 mm). Coupling 3D culture and perfusion flow leads to the creation of a more biomimetic environment. We examined the ability of the bioreactor to maintain cell viability outside of an incubator environment (temperature and pH stability), investigated the flow features of the system (flow induced shear stress), and determined the image quality in order to perform time-lapsed imaging of two-dimensional (2D) and 3D cell culture. In situ imaging was performed on 2D and 3D, culture samples and cell viability was measured under perfusion flow (2.5 mL/min, 0.016 Pa). The visualization of cell response to their environment, in real time, will help to further elucidate the influences of biomaterial surface features, scaffold architectures, and the influence of flow induced shear on cell response and growth of new tissue.

Animals↗

Sentinel lymph node biopsy for melanoma.

BACKGROUND: The most powerful predictor of survival for patients with melanoma is the status of the regional lymph nodes. Sentinel lymph node biopsy may provide improved staging accuracy without the morbidity of elective lymph node dissection (ELND). METHODS: Sixty-eight patients with intermediate thickness melanoma underwent gamma probe guided sentinel node biopsy without ELND and were followed up over a mean of 22 months. RESULTS: A sentinel node was found in all patients. Six patients (9%) had positive sentinel nodes; all underwent complete lymphadenectomy. Two patients (3%) with negative sentinel nodes developed nodal recurrence; 1 of these patients was found to have microscopic disease on reexamination of the sentinel node. Two patients (3%) developed systemic disease. CONCLUSION: Gamma probe guided sentinel node biopsy can be performed with a high rate of technical success. It provides accurate pathological staging with a low incidence of nodal basin failure.

Adult↗

Sampling for formaldehyde in workplace and ambient air environments--additional laboratory validation and field verification of a passive air monitoring device compared with conventional sampling methods.

Results of three extensive plant field tests using both area and personal sampling and involving 51 sets of comparison samples show the Du Pont Pro-Tek Formaldehyde Badge to have excellent correlation with three commonly used formaldehyde monitoring methods. In addition, comprehensive laboratory validation tests are reported which confirm an overall accuracy of +/- 9.6 to +/- 11.6% for the badge over an exposure range of 0.12-6.8 ppm. Laboratory test data are also included showing that the badge: (1) meets NIOSH and OSHA accuracy requirements of less than or equal to +/- 25% down to 1.6 ppm-hours (200 ppb) for an 8-hour TWA exposure; (2) is capable of accurately sampling for 15-minute exposures; and (3) is not affected by pressure or relative humidity variations.

Air Pollutants, Occupational↗

Noxythiolin--high-performance liquid chromatographic assay and stability.

A rapid stability-indicating high-performance liquid chromatographic assay for noxythiolin has been developed and its application to the determination of the shelf-life of solid and solution forms is illustrated. Kinetic models which describe the degradation profile have been evaluated and concentrated solutions are modelled by a A B + C system whereas more dilute solutions approximate to the A B or limiting first-order case.

Chemical Phenomena↗

Compensating the medical group executive.

True commitment and top executive performance can best be achieved through a combination of making the right hiring decision, providing appropriate authority, developing a trusting relationship, and providing appropriate compensation.

Employee Incentive Plans↗