Fractalkine is a recently identified chemokine that exhibits cell adhesion and chemoattractive properties. It represents a unique member of the chemokine superfamily because it is located predominantly in the brain in which it is expressed constitutively on specific subsets of neurons. To elucidate the possible role of neuronally expressed fractalkine in the inflammatory response to neuronal injury, we have analyzed the regulation of fractalkine mRNA expression and protein cleavage under conditions of neurotoxicity. We observed that mRNA encoding fractalkine is unaffected by experimental ischemic stroke (permanent middle cerebral artery occlusion) in the rat. Similarly, in vitro, levels of fractalkine mRNA were unaffected by ensuing excitotoxicity. However, when analyzed at the protein level, we found that fractalkine is rapidly cleaved from cultured neurons in response to an excitotoxic stimulus. More specifically, fractalkine cleavage preceded actual neuronal death by 2-3 hr, and, when evaluated functionally, fractalkine represented the principal chemokine released from the neurons into the culture medium upon an excitotoxic stimulus to promote chemotaxis of primary microglial and monocytic cells. We further demonstrate that cleavage of neuron-derived, chemoattractive fractalkine can be prevented by inhibition of matrix metalloproteases. These data strongly suggest that dynamic proteolytic cleavage of fractalkine from neuronal membranes in response to a neurotoxic insult, and subsequent chemoattraction of reactive immune cells, may represent an early event in the inflammatory response to neuronal injury.

The rota-rod and grid-walking tests of motor performance provide quantitative, objective, and reproducible measures of functional impairment of rats following an ischemic insult. These impairments correlate directly with infarct volume and provide information integral to future studies evaluating the effects of potential neuroprotective agents.

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Thermochron iButtons incorporate the latest in digital technology, making them smaller, less expensive, durable and potentially more reliable than many other temperature logging devices. The objective of this study was to test the accuracy of an inexpensive air temperature measurement system, composed of a Thermochron iButton and radiation shield. Sixty-one iButtons were subjected to a sequence of two water baths (0°C and 24·9°C) to assess the absolute accuracy of the sensors. Five solar radiation shields were tested in a greenhouse setting to evaluate the reduction in radiative heating. Significant differences (p < 0·05) were detected between instruments subsequent to both water-bath treatment analyses. The accuracy of the sensors was well within the manufacturer's stated specification of ±1·0°C with a collective temperature variance of ±0·21°C. Temperature responses generated by the Thermochron iButtons in different radiation shields were consistent, but varied significantly (p < 0·05) from 28 to 44°C based on diurnal temperature ranges. Results indicate that the Thermochron iButton is an accurate, inexpensive alternative to more expensive temperature datalogging systems, and is well suited for obtaining quality spatially distributed data for hydrologic and water quality investigations.