A stable and productive marine microbial community was sustained through the end-Devonian Hangenberg Crisis within the Cleveland Shale of the Appalachian Basin, United States

The end-Devonian Hangenberg Crisis constituted one of the greatest ecological and environmental perturbations of the Paleozoic Era. To date, however, it has been difficult to precisely constrain the occurrence of the Hangenberg Crisis in the Appalachian Basin of the United States and thus to directly assess the effects of this crisis on marine microbial communities and paleoenvironmental conditions. Here, we integrate organic and inorganic chemostratigraphic records compiled from two discrete outcrop locations to characterize the onset and paleoenvironmental transitions associated with the Hangenberg Crisis within the Cleveland Shale member of the Ohio Shale. The upper Cleveland Shale records both positive carbon (δ¹³ C_org ) and nitrogen (δ¹⁵ N_total ) isotopic excursions, and replenished trace metal inventories with links to eustatic rise. These dual but apparently temporally offset isotope excursions may be useful for stratigraphic correlation with other productive end-Devonian epeiric marine locations. Deposition of the black shale succession occurred locally beneath a redox-stratified water column with euxinic zones, with signs of strengthening denitrification during the Hangenberg Crisis interval, but with an otherwise stable and algal-rich marine microbial community structure sustained in the surface mixed layer as ascertained by lipid biomarker assemblages. Discernible trace fossil signals in some horizons suggest, however, that bioturbation and seafloor oxygenation occurred episodically throughout this succession and highlight that geochemical proxies often fail to capture these rapid and sporadic redox fluctuations in ancient black shales. The paleoenvironmental conditions, source biota, and accumulations of black shale are consistent with expressions of the Hangenberg Crisis globally, suggesting this event is likely captured within the uppermost strata of the Cleveland Shale in North America.

Sulfasalazine-induced hepatotoxicity in children with inflammatory bowel disease

A case of severe sulfasalazine-induced hepatotoxicity is reported in a 14-year-old girl with Crohn's disease. Fourteen days after beginning sulfasalazine, she developed a systemic reaction characterized by high fever, maculopapular rash, lymphadenopathy, abdominal pain, and malaise, with tender hepatomegaly and elevated liver functions, leukemoid reaction, with eosinophilia, and immune complexes. She responded promptly to high-dose intravenous steroids with complete recovery. This case was compared to the three similar pediatric cases in the literature. The latent period was 11-19 days between sulfasalazine therapy and the onset of high fever, generalized lymphadenopathy, and pruritic maculopapular rash that spared palms and soles and resolved with desquamation. All children had hepatotoxicity indicated by tender hepatomegaly, elevated liver enzymes, and histologic inflammation on liver biopsy. The similarity between these features and those of other sulfa-induced hepatotoxic reactions suggests that the sulfapyridine moiety is the etiologic agent in these hypersensitivity reactions. Those children with circulating immune complexes responded well to steroids. Proper therapy for this rare but severe idiosyncratic reaction includes prompt recognition and discontinuation of sulfasalazine, and high-dose corticosteroid therapy.