We use survey data from all accepted applicants to Teach for America 1993-98 to assess the longer-term effect of youth service on participants' current civic attitudes and behaviors. While TFA "graduates" score higher than the two comparison groups -"dropouts" and "non-matriculants" -on a broad range of attitudinal items measuring civic commitment, these differences appear to be less a byproduct of the TFA experience than a reflection of current involvement with the TFA organization. Moreover, the attitudinal differences are not reflected in actual civic behavior. Specifically, graduates lag behind non-matriculants in current service activity and generally trail both nonmatriculants and drop-outs in self-reported participation in five other forms of civic/ political activity measured in the study. Graduates also vote at lower rates than the other two groups. Finally, fewer graduates report employment in "pro-social" jobs than either non-matriculants or drop-outs. We close by speculating on what mechanisms may help explain variation in the long-term effects of youth service or activist experiences.
1. Irradiation with three short ultraviolet (UV) wave lengths, 226, 233, and 239 mµ rapidly immobilizes Paramecium caudatum, the dosage required being smaller the shorter the wave length. 85 per cent of paramecia immobilized with wave length 226 mµ recover completely. Recovery from immobilizing doses is less the longer the wave length. 2. Irradiation continued after immobilization kills the paramecia in a manner which is markedly different for very short (226, 233, and 239 mµ) and longer (267 mµ) wave lengths. 3. An action spectrum for immobilization in P. caudatum was determined for the wave lengths 226, 233, 239, 248, and 267 mµ, and found to resemble the absorption of protein and lipide in the wave length region below 248 mµ. Addition of these data to those of Giese (1945 b) gives an action spectrum resembling the absorption by albumin-like protein. 4. Division of P. caudatum is delayed by doses of wave lengths 226, 233, and 239 mµ which cause immobilization, the longest wave length being most effective. 5. Immobilization at any of the wave lengths tested (226, 233, 239, 248, 267 mµ) is not photoreversible when UV-treated paramecia are concurrently illuminated. 6. Division delay resulting from immobilizing doses of 226, 233, and 239 mµ is photoreversible by exposure to visible light concurrently with the UV. 7. Division delay induced by exposure to wave length 267 mµ is reduced by exposure to visible light applied concurrently with UV or immediately afterwards. 8. The data suggest that the shortest UV wave length tested (226 mµ) affects the cytoplasm selectively, because it is absorbed superficially as indicated by unilateral fluorescence in UV. Consequently it immobilizes paramecia rapidly but has little effect on the division rate because little radiation reaches the nucleus. 9. The data support the view that nuclear effects of UV are readily photoreversed but cytoplasmic effects are not.
The degree of photoreactivation or rever"~al of injurious effects of ultraviolet radiations (UV) by illumination with visible light has been shown to increase with length of exposure of the irradiated organisms to visible light (Dulbecco, 1949; Kelner, 1951). After maximal photoreactivation of phage has been achieved, further illumination with whitelight has no further effect (Dulbecco, 1949), whereas in EsckericMa coli and Streptomyces griseus additional illumination proved to be injurious in some cases (Keiner, 1951). Photoreactivation in Colpidium coIpod~ increases with exposure to monochromatic or mixed visible light to a maximal value. Additional illumination to the extent previously tried was not injurious (Giese, Brandt, Iverson, and Wells, 1952). The question arises as to how many quanta of visible light are necessary to reverse maximally the action of 1 quantum of UV. This information would be interesting for theoretical reasons. The present report records such determinations for Colpidium colpoda, a ciliate protozoan. Metkods and MaterialsAs a criterion of UV injury the retardation of the third division of the irradiated colpidia was determined in much the same way as in previous experiments with paramecia (Giese, 1939). Photoreversal was measured by recovery from such division delay.Fortunately Colpidiura colpoda like Paramecium caudatura (Giese, 1939(Giese, , 1945 does not show a period of cessation of division after UV treatment as does P. aurdia or P. mul~iraicronucleatura (Giese and Reed, 1940;Kimball and Gaither, 1951) or Tarahymena geleii (Christensen, unpublished). Therefore the delay in the third division after irradiation may be determined without this complication. The methods were in general similar to those described in the previous paper . (Giese, Brandt, Iverson, and Wells, 1952).As a source of radiation a quartz mercury arc was used and the radiations were passed through a natural quartz monochromator. The 2654 A line in the short UV was reflected by a fight angle quartz prism upon the horizontally held quartz cell containing the protozoa. For photoreactivation the light from a high pressure Ames
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.