Chronic, topical exposure to benzo[a]pyrene induces relatively high steady-state levels of DNA adducts in target tissues and alters kinetics of adduct loss.

Carcinogen-DNA adduct measurements may become useful biomarkers of effective dose and/or early effect. However, validation of this biomarker is required at several levels to ensure that human exposure and response are accurately reflected. Important in this regard is an understanding of the relative biomarker levels in target and nontarget organs and the response of the biomarker under the chronic, low-dose conditions to which humans are exposed. We studied the differences between single and chronic topical application of benzo[a]pyrene (BAP) on the accumulation and removal of BAP-DNA adducts in skin, lung, and liver. Animals were treated with BAP at 10, 25, or 50 nMol topically once or twice per week for as long as 15 weeks. Animals were sacrificed either at 24, 48, or 72 hr after the last dose at 1 and 30 treatments, and after 24 hr for all other treatment groups. Adduct levels increased with increasing dose, but the slope of the dose-response was different in each organ. At low doses, accumulation was linear in skin and lung, but at high doses the adduct levels in the lung increased dramatically at the same time when the levels in the skin reached apparent steady state. In the liver adduct, levels were lower than in target tissues and apparent steady-state adduct levels were reached rapidly, the maxima being independent of dose, suggesting that activating metabolism was saturated in this organ. Removal of adducts from skin, the target organ, was more rapid following single treatment than with chronic exposure. This finding is consistent with earlier data, indicating that some areas of the genome are more resistant to repair. Thus, repeated exposure and repair cycles would be more likely to cause an increase in the proportion of carcinogen-DNA adducts in repair-resistant areas of the genome. These findings indicate that single-dose experiments may underestimate the potential for carcinogenicity for compounds that follow this pattern.

Oxidation states of the manganese cluster during the flash-induced S-state cycle of the photosynthetic oxygen-evolving complex.

The Mn K-edge x-ray absorption spectra for the pure S states of the tetranuclear Mn cluster of the oxygen-evolving complex of photosystem II during flash-induced S-state cycling have been determined. The relative S-state populations in samples given 0, 1, 2, 3, 4, or 5 flashes were determined from fitting the flash-induced electron paramagnetic resonance (EPR) multiline signal oscillation pattern to the Kok model. The edge spectra of samples given 0, 1, 2, or 3 flashes were combined with EPR information to calculate the pure S-state edge spectra. The edge positions (defined as the zero-crossing of the second derivatives) are 6550.1, 6551.7, 6553.5, and 6553.8 eV for S0, S1, S2, and S3, respectively. In addition to the shift in edge position, the S0--> S1 and S1--> S2 transitions are accompanied by characteristic changes in the shape of the edge, both indicative of Mn oxidation. The edge position shifts very little (0.3 eV) for the S2--> S3 transition, and the edge shape shows only subtle changes. We conclude that probably no direct Mn oxidation is involved in this transition. The proposed Mn oxidation state assignments are as follows: S0 (II, III, IV, IV) or (III, III, III, IV), S1 (III, III, IV, IV), S2 (III, IV, IV, IV), S3 (III, IV, IV, IV).

Policy Changes to the Federal and State Management of Subsistence Hunting and Fishing in Alaska

Subsistence in Alaska is currently being impacted by naturally occurring factors such as global warming, species migration shifts, and the declination of fishery and wildlife populations. Not only are external factors pressuring the debate, management strategies from the dual management operation appear to have failed. The current national focus has been centered on federal policy changes regarding subsistence. This project extends the federal subsistence review process into the state management of subsistence and provides practical solutions for enhancing both policy programs.

Bulletin of the Illinois State Laboratory of Natural History.

7 (1904 - 1909)

Memorial to the Harvard Board of Overseers, 1822 April

Two drafts of a letter.

Memorial to the Harvard Board of Overseers, 1823 November 3

Five drafts of a letter.

Minutes of the Proceedings of the Board of Overseers of Harvard College, 1775-1776

This is a small, paper-bound "waste book" containing minutes taken by the Secretary pro tempore, Samuel Cooke, at meetings held on the following dates: July 31, 1775; August 8, 1775; August 22, 1775; September 5, 1775; October 3, 1775; October 23, 1775 (fragmentary); November 5, 1775; April 16, 1776; and April 23, 1776. Because these meetings took place during the American Revolutionary War, they were held in the "Council chamber at Watertown."

Annual report of the Director to the Board of Trustees for the year ... / Field Museum of Natural History

9, no. 2

Annual report of the Director to the Board of Trustees for the year ... / Field Museum of Natural History

10, no. 2

Annual report of the Director to the Board of Trustees for the year ... / Field Museum of Natural History

5, no. 6

Annual report of the Director to the Board of Trustees for the year ... / Field Museum of Natural History

6, no. 1

Annual report of the Director to the Board of Trustees for the year ... / Field Museum of Natural History

3, no. 2

Annual report of the Director to the Board of Trustees for the year ... / Field Museum of Natural History

7, no. 3

Annual report of the Director to the Board of Trustees for the year ... / Field Museum of Natural History

3, no. 4

Annual report of the Director to the Board of Trustees for the year ... / Field Columbian Museum.

2, no. 4