Confocal pattern period in multiple-aperture confocal imaging systems with coherent illumination.

We have built a programmable multiple-aperture confocal imaging system that uses a spatial light modulator (a Texas Instruments digital micromirror device). Excellent axial resolution and confocal imaging quality have been experimentally demonstrated with this system, even when the distance between adjacent ON pixels is four times the size of the pixel aperture. By contrast, typical pinhole-based systems (e.g., a Nipkow disk) employ an adjacent aperture distance-to-size ratio of 10x . We have achieved improvement over such systems by 6.25x in both light-utilization efficiency and confocal image rate without adding more components and extra processing time.

Effects of unilateral and bilateral auricular transcutaneous electrical nerve stimulation on cutaneous pain threshold.

This study compared the effects of unilateral and bilateral auricular transcutaneous electrical nerve stimulation on cutaneous pain threshold. Auricular acupuncture points were stimulated with low frequency, high intensity TENS for 45 seconds. Sixty healthy, adult subjects were assigned randomly to one of two treatment groups or to a control group. The two treatment groups received low frequency, high intensity TENS either unilaterally or bilaterally. The control group did not receive auricular stimulation. Experimental pain threshold at the left wrist was determined with a painful stimulus before and after auricular stimulation. Both unilateral and bilateral auricular stimulation groups exhibited a significant increase (p less than .05) in experimental pain threshold, but the control group did not. The mean change values between the unilateral and bilateral stimulation groups were not statistically different. These results suggest that both unilateral and bilateral auricular TENS can increase pain threshold.

Fluorescent erythrosin B is preferable to trypan blue as a vital exclusion dye for mammalian cells in monolayer culture.

Erythrosin B and trypan blue are tested and compared for their effectiveness as vital exclusion stains for mammalian cells in monolayer culture. Both stains are supposed to mark cells that have lost membrane integrity. Fluorescein diacetate (FDA), an efficient vital inclusion stain, is used as a control, as it marks cells retaining membrane integrity. Erythrosin B and FDA are used as fluorescent dyes, whereas trypan blue colors via light absorption. The effectiveness of both vital exclusion stains is assayed by their ability to stain a high percentage of monolayer cells exposed to treatments lethal to an entire cell population. Two types of lethal treatment, severe heat and metabolic poison, are employed. Erythrosin B stains all monolayer cells immediately after complete lethal treatment. Trypan blue optimally stains only about 60% of monolayer cells. Cell staining by erythrosin B and by FDA are found to be mutually exclusive. This result demonstrates the coincidence of viability indications by erythrosin B and FDA and thus confirms the reliability of both viability stains as they probe membrane permeability via independent mechanisms. This study shows that erythrosin B is an effective, nontoxic, and convenient fluorescent vital exclusion dye for three mammalian cell lines in monolayer culture, but tends to disqualify trypan blue for this application.