Tarsal and tarsometatarsal coalitions from Mound C (Ocmulgee Macon Plateau site, Georgia): implications for understanding the patterns, origins, and antiquity of pedal coalitions in Native American populations.

Tarsal and tarsometatarsal coalitions are malsegmentation errors that result in incomplete division between two or more normally separate bones of the foot. Coalitions may be osseous, characterized by bony union, or non-osseous, in which the affected elements are united by fibrous tissue, cartilage, or some combination of both. Evidence indicates that non-osseous coalitions are frequently overlooked or misinterpreted in skeletal samples. The purpose of this study is to (1) report two non-osseous coalition cases (naviculocuneiform I, CF3-MT3) from the Ocmulgee Mound Site in Georgia, and (2) examine the occurrence of coalitions throughout the foot in Native American samples relative to other major populations. Evidence suggests that Native Americans exhibit a pattern of coalitions in the foot that differs from that recently documented for European and African samples. Native Americans display a relatively high rate of midfoot and forefoot coalitions, and known cases are both geographically and temporally diverse. This distribution, along with evidence of similar patterns in East Asian samples, suggests that the pattern of coalition seen in Native Americans has origins in Asiatic parent populations during the late Pleistocene. Individuals migrating to the New World with proximal midfoot coalitions are likely to have endured biomechanical stress during prolonged physical activity and walking, as frequently seen in modern clinical cases.

The electrophile counterattack response: protection against neoplasia and toxicity.

Exposure of rodents or their cells in culture to low doses of a wide variety of chemical agents, many of which are electrophiles, evokes a coordinated metabolic response that protects these systems against the toxicity (including mutagenicity and carcinogenicity) of higher doses of the same or other electrophiles. This response involves enhanced transcription of Phase 2 enzymes: glutathione transferases, NAD(P)H:quinone reductase, UDP-glucuronsyltransferases, and epoxide hydrolase, as well as the elevation of intracellular levels of reduced glutathione. We suggest that this cellular adaptation, which occurs in the liver and many peripheral tissues, be designated as the "Electrophile Counterattack" response. Seven families of highly diverse chemical agents that elicit this response include: oxidatively labile diphenols and quinones; Michael reaction acceptors (olefins conjugated to electron-withdrawing groups); isothiocyanates; organic hydroperoxides; vicinal dimercaptans; trivalent arsenicals; heavy metals (HgCl2, CdCl2) as well as mercury derivatives with high affinities for sulfhydryl groups; and 1,2-dithiole-3-thiones. An analysis of the molecular mechanisms of these enzyme inductions was carried out by transient expression in hepatoma cells of a plasmid containing a 41-bp enhancer element derived from the 5'-upstream region of the mouse glutathione transferase Ya gene, and the promoter region of this gene, linked to a human growth hormone reporter gene. The concentrations of 28 inducers (belonging to the seven chemical classes) required to double growth hormone production in this system spanned a range of four orders of magnitude and were closely and linearly correlated with the concentrations of the same compounds required to double the specific activity of quinone reductase in murine hepatoma cells. We therefore conclude that the regulation of these Phase 2 enzymes (and possibly also that of glutathione synthesis) by all of these inducers is mediated by the same enhancer element that contains AP-1-like sites. Similar enhancer sequences are present in the rat glutathione transferase Ya gene, and in the upstream regulatory regions of the quinone reductase genes of rat and human liver.

Induction of glutathione transferases and NAD(P)H:quinone reductase by fumaric acid derivatives in rodent cells and tissues.

Dimethyl fumarate and dimethyl maleate are potent inducers of cytosolic NAD(P)H:(quinone acceptor) oxidoreductase (here designated quinone reductase) activity in Hepa 1c1c7 murine hepatoma cells in culture, whereas fumaric and maleic acids are much less potent, in agreement with the much greater reactivity of the esters as Michael reaction acceptors (P. Talalay, M. J. De Long, and H. J. Prochaska, Proc. Natl. Acad. Sci. USA, 85:8261-8265, 1988). Dimethyl fumarate also induced quinone reductase in mutants of the Hepa 1c1c7 cell line that were either defective in the Ah receptor or in cytochrome P1-450 activity, thereby establishing that this compound is a monofunctional inducer (H. J. Prochaska and P. Talalay, Cancer Res., 48: 4776-4782, 1988). Addition of dimethyl fumarate to the diet of female CD-1 mice and female Sprague-Dawley rats at 0.2-0.5% concentrations elevated cytosolic glutathione transferases and quinone reductase activities in a variety of organs, whereas much higher concentrations of fumaric acid were only marginally active. The widespread induction of such detoxication enzymes by dimethyl fumarate suggests the potential value of this compound as a protective agent against chemical carcinogenesis and other forms of electrophile toxicity. This proposal is supported by the finding that the concentrations of dimethyl fumarate required to obtain substantial enzyme inductions were well tolerated by rodents. Furthermore, the parent fumaric acid has low chronic toxicity and is a naturally occurring metabolic intermediate that is already in the food chain as an additive, and fumarate salts and esters are used for therapeutic purposes in man.