Abstract
Cellular autofluorescence spectra were monitored in a single-beam gradient force optical trap ("optical tweezers") in order to probe the physiological effects of near infrared and UVA (320-400 nm) microirradiation. Prior to trapping, Chinese hamster ovary cells exhibited weak UVA-excited autofluorescence with maxima at 455 nm characteristic of beta-nicotinamide adenine dinucleotide (phosphate) emission. No strong effect of a 1064 nm NIR microbeam on fluorescence intensity and spectral characteristics was found during trapping, even for power densities up to 70 MW/cm2 and radiant exposures of 100 GJ/cm2. In contrast to the 1064 nm trap, a 760 nm trapping beam caused a two-fold autofluorescence increase within 5 min (about 20 GJ/cm2). Exposure to 365 nm UVA (1 W/cm2) during 1064 nm trapping significantly altered cellular autofluorescence, causing, within 10 min, a five-fold increase and a 6 nm red shift versus initial levels. We conclude that 1064 nm microbeams can be applied for an extended period without producing autofluorescence changes characteristic of alterations in the cellular redox state. However, 760 nm effects may occur via a two-photon absorption mechanism, which, in a manner similar to UVA exposure, alters the redox balance and places the cell in a state of oxidative stress.
Highlights
Resistance to pneumococcal infection was tested in T-lymphocyte-deficient, nude mice
T-lymphocytes do not appear to play a significant role in the host's defense against the pneumococcus
Resistance to infection with the pneumococcus (Streptococcus pneumoniae) is a complex process known to involve a number of different aspects of immunity
Summary
INFECTION AND IMMUNITY, Nov. 1975, p. 1222-1223 Copyright Resistance to pneumococcal infection was tested in T-lymphocyte-deficient, nude (nu/nu) mice. Pneumococcal serum opsonizing activity, in vivo phagocytosis of the pneumococcus, and the mean lethal dose for the pneumococcus were all found to be the same in nude mice as in control (+/+) mice. It provides the opportunity to study directly, and in vivo, the role of T-lymphocytes in the host's defense against pneumococcal infections. Pneumococcal opsonizing activity was measured in the pooled serum of nude mice. 1.25 x 10W exudate leukocytes obtained from Swiss-Webster mice and 6.25 x 108 log-phase type 25 pneumococci were added to the desired dilution of pooled test serum and the mixture was rotated at 12 rpm at 37 C for 30 min [9]. It should be noted that the cumulative mortality was the same in the two groups on each day of the LD50 study
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