Gas chromatography: an investigative tool in multiple allergies to essential oils.

Essential or fragrant oils are volatile odourous mixtures of organic chemical compounds that are widely used in aromatherapy and in the perfume industry. Because of their frequent use, allergy to essential oils is being increasingly recognized. We report 2 cases of multiple allergies to essential oils in professional aromatherapists. Gas chromatography/mass spectrometry was used to analyse the oils in order to identify a common allergen responsible for the contact dermatitis. In both the cases, alpha- and beta-pinene were found to be the most common constituent in the oils and thus appeared to be key allergens. alpha-pinene was confirmed as an allergen on repeat patch testing with pure alpha-pinene in both cases. 12 controls tested were negative for the same. Gas chromatography-mass spectrometry was found to be an extremely useful tool that could be utilized in investigating multiple allergies to essential oils.

Structural abnormalities do not explain the early functional abnormalities in the peripheral nerves of the streptozotocin diabetic rat.

The streptozotocin (STZ)-diabetic rat, the most commonly employed model of experimental diabetic neuropathy, is characterised by a reduction in nerve conduction velocity, pain threshold and blood flow. Whether or not structural abnormalities underlie these functional abnormalities is unclear. 10 adult male Sprague-Dawley STZ-diabetic rats (diabetes duration 27 d) and 10 age-matched (23 wk) control animals were studied. Motor nerve conduction velocity (m s(-1)) was significantly reduced in diabetic (41.31 +/- 0.8) compared with control (46.15 +/- 1.5) animals (P < 0.001). The concentration of sciatic nerve glucose (P < 0.001), fructose (P < 0.001) and sorbitol (P < 0.001) was elevated, and myoinositol (P < 0.001) was reduced in diabetic compared with control animals. Detailed morphometric studies demonstrated no significant difference in fascicular area, myelinated fibre density, fibre and axon areas as well as unmyelinated fibre density and diameter. Endoneurial capillary density, basement membrane area and endothelial cell profile number did not differ between diabetic and control animals. However, luminal area (P < 0.03) was increased and endothelial cell area (P < 0.08) was decreased in the diabetic rats. We conclude there is no detectable structural basis for the reduction in nerve conduction velocity, pain threshold or blood flow, observed in the streptozotocin diabetic rat.

Functional magnetic resonance imaging of median nerve stimulation in rats at 2.0 T.

An animal model of sensory activation using fMRI at 2.0 T has been developed, demonstrating that fMRI studies on animals need not be limited to high field magnets. These methods produced reliable image intensity changes of 2% using median nerve stimulation in rats at 3 Hz and propofol as the anesthetic agent. At 6 Hz the activation was slightly but not statistically significantly greater. The feasibility of fMRI studies in animals using propofol suggests that it may be a useful anesthetic for fMRI studies in agitated adult patients or in children.