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Biomedical subjects

N J Chaffey

Publications and source records attributed to N J Chaffey.

6 recordsLinked to original sources
PubMed1997

Visualization of the cytoskeleton within the secondary vascular system of hardwood species.

A single fixation technique has been devised to demonstrate localization of alpha-tubulin (for microtubules) and F-actin (for microfilaments) within the secondary vascular system of hardwood trees by indirect immunofluorescence microscopy using butyl-methylmethacrylate-embedded material. Application of this technique to problems of cytomorphogenesis during secondary growth and its versatility are demonstrated with the hardwood species Aesculus hippocastanum L., Salix viminalis L., S. burjatica Nazarov x S. viminalis L., Hedera helix L., Acer platanoides L., Platanus sp., Quercus ilex L. and Liriodendron tulipifera L., and in the softwood Pinus pinea L. The methods employed have considerable scope for advancing knowledge of the role of the cytoskeleton in differentiation within the secondary vascular system of woody species.

Actins↗
PubMedDate not supplied

A preliminary report on a new hydraulic sphincter for controlling urinary incontinence.

A new pressure-regulated artificial urinary sphincter (AUS) has been developed which overcomes many of the deficiencies of earlier devices. This implantable AUS comprises a circular occluder cuff and the means to inflate and deflate through a pressure-regulated valve. The device is made from medical-grade silicone rubber and filled with radio-opaque isotonic fluid. A few days before surgery the implant is coated on the outside with an antibiotic-loaded silicone rubber solution. Tests have shown that the regulated pressure was very easily adjusted in situ by injecting or withdrawing the hydraulic fluid through a hypodermic needle penetrating a self-sealing filling port. When set, the regulated pressure remained very stable. The mechanism by which cuff pressure was increased to overcome stress incontinence worked well. Of the five earlier devices (AUS Mk I) implanted, none has survived without mechanical failure. The two latest implants (Mk II), which were rigorously tested for defects before implantation, have been more successful.

Adolescent↗
PubMedDate not supplied

Controlling radio frequency interference from neurological prostheses.

The simplest kind of radio frequency (RF) coupled neurological prosthesis, in which a burst of RF, generated by the external equipment, provides the stimulus energy via a passive implanted receiver, is the most troublesome in respect of RF interference (RFI). Because the low ratio of pulse duration to interpulse interval is usually the case, the peak power transmitted is necessarily high, of the order of watts. This paper outlines a series of measurements by which the mode of RFI generation by a typical external equipment was precisely identified, enabling rational and appropriate countermeasures to be taken.

Electric Stimulation↗
PubMedDate not supplied

Rapid communication: cleaning up a Hartley oscillator.

In a programme to understand, and learn to control, radiofrequency interference from neurological prostheses, it was discovered that a harmless-looking Hartley oscillator (one type of harmonic oscillator) generated a forest of harmonics extending to 1 GHz. These harmonics were not difficult to eliminate. The point of this paper is to emphasize that, given the selection of instruments used by most development engineers, the harmonics would probably have been missed.

Prostheses and Implants↗