Late Pleistocene proboscidean population dynamics in the North American Midcontinent

Understanding megafaunal population dynamics is critical to testing and refining scenarios of how extinctions occurred during the terminal Pleistocene. Large-scale, collections-based, chronological, and taphonomic analyses of midwestern Proboscidea suggest divergent population histories in mammoths and mastodons after the Last Glacial Maximum (LGM). Although extinction of both taxa occurred in the very late Bølling-Allerød (B-A) or early Younger Dryas (YD), Mammuthus is dominant during the LGM with a decreasing presence in the region until extirpation. Mammut americanum however, is absent during the LGM but becomes the dominant taxon during the subsequent B-A. Trace and physical evidence of large carnivores in post-LGM proboscidean assemblages is extremely rare, suggesting apex predators had minimal impact on mammoth and mastodon populations at this time. The ultimate mechanism(s) of extinction remain unclear; however, the wide geographic distribution of late Mammut and an increase in the frequency of multi-animal death assemblages is consistent with a large, destabilized population experiencing periodic boom-bust cycling at the end of the B-A. We suggest this pattern is due to the collapse of trophic controls on proboscidean populations prior to the LGM and a subsequent system-wide shift from top-down to bottom-up regulatory mechanisms in Proboscidea

Cotranslational protein assembly imposes evolutionary constraints on homomeric proteins

Cotranslational protein folding can facilitate rapid formation of functional structures. However, it might also cause premature assembly of protein complexes, if two interacting nascent chains are in close proximity. By analyzing known protein structures, we show that homomeric protein contacts are enriched towards the C-termini of polypeptide chains across diverse proteomes. We hypothesize that this is the result of evolutionary constraints for folding to occur prior to assembly. Using high-throughput imaging of protein homomers in vivo in E. coli and engineered protein constructs with N- and C-terminal oligomerization domains, we show that, indeed, proteins with C-terminal homomeric interface residues consistently assemble more efficiently than those with N-terminal interface residues. Using in vivo, in vitro and in silico experiments, we identify features that govern successful assembly of homomers, which have implications for protein design and expression optimization

Deconstructing tumor heterogeneity: the stromal perspective.

Significant advances have been made towards understanding the role of immune cell-tumor interplay in either suppressing or promoting tumor growth, progression, and recurrence, however, the roles of additional stromal elements, cell types and/or cell states remain ill-defined. The overarching goal of this NCI-sponsored workshop was to highlight and integrate the critical functions of non-immune stromal components in regulating tumor heterogeneity and its impact on tumor initiation, progression, and resistance to therapy. The workshop explored the opposing roles of tumor supportive versus suppressive stroma and how cellular composition and function may be altered during disease progression. It also highlighted microenvironment-centered mechanisms dictating indolence or aggressiveness of early lesions and how spatial geography impacts stromal attributes and function. The prognostic and therapeutic implications as well as potential vulnerabilities within the heterogeneous tumor microenvironment were also discussed. These broad topics were included in this workshop as an effort to identify current challenges and knowledge gaps in the field

Nutrient survey of Arizona cotton with reference to soil type and water quality

Established cotton fields in 6 counties were sampled during the 1981 growing season. Two composite soil samples were taken from each field and both leaf blade and petiole tissue samples were taken two times during the growing season. Irrigation water samples were also taken. The tissue samples were analyzed for 13 elements, and the soil samples analyzed for 9 element, in addition, PH, EC, CEC and percent saturation values were determined on the soil samples. The level of each plant and soil element was investigated and compared with published critical and/or sufficiency levels. Simple correlation analysis were done between plant data and between plant and soil data. Phosphorus NO₃ and B were low and some samples were low in Zn. Calcium, Mg, K, and Fe levels were adequate and no unusual levels of AL and Ba were found. Some samples contained high levels of Na.hydrology collectio

Late Pleistocene proboscidean population dynamics in the North American Midcontinent

Understanding megafaunal population dynamics is critical to testing and refining scenarios of how extinctions occurred during the terminal Pleistocene. Large-scale, collections-based, chronological, and taphonomic analyses of midwestern Proboscidea suggest divergent population histories in mammoths and mastodons after the Last Glacial Maximum (LGM). Although extinction of both taxa occurred in the very late Bølling-Allerød (B-A) or early Younger Dryas (YD), Mammuthus is dominant during the LGM with a decreasing presence in the region until extirpation. Mammut americanum however, is absent during the LGM but becomes the dominant taxon during the subsequent B-A. Trace and physical evidence of large carnivores in post-LGM proboscidean assemblages is extremely rare, suggesting apex predators had minimal impact on mammoth and mastodon populations at this time. The ultimate mechanism(s) of extinction remain unclear; however, the wide geographic distribution of late Mammut and an increase in the frequency of multi-animal death assemblages is consistent with a large, destabilized population experiencing periodic boom-bust cycling at the end of the B-A. We suggest this pattern is due to the collapse of trophic controls on proboscidean populations prior to the LGM and a subsequent system-wide shift from top-down to bottom-up regulatory mechanisms in Proboscidea.This is the peer reviewed version of the following article: Widga, Chris, Stacey N. Lengyel, Jeffrey Saunders, Gregory Hodgins, J. Douglas Walker, and Alan D. Wanamaker. "Late Pleistocene proboscidean population dynamics in the North American Midcontinent." Boreas 46, no. 4 (2017): 772-782, which has been published in final form at doi: 10.1111/bor.12235. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.</p

MagIC as a FAIR Repository for America\u27s Directional Archaeomagnetic Legacy Data

Beginning in 1964, an academic lineage of Robert DuBois and his students, Daniel Wolfman and Jeffrey Eighmy, developed dedicated United States-based archaeomagnetic research programs. Collectively, they analyzed over 5,377 archaeomagnetic sites, primarily from North America, dated to less than 2,000 years old. Yet despite their decades of effort, few journal publications resulted. Most of their published results are embedded in archeological reports, often without technical data, which limits the data\u27s accessibility. Furthermore, when published, the results are generally averaged at the site level using statistical conventions different from today\u27s standards, limiting the data\u27s comparability and (re)usability. In 2015, we undertook a salvage archival study to digitize the surviving data and metadata from the scientists\u27 individual estates and emeritus collections. We digitized measurement data from more than 51,000 specimens, reinterpreted them using modern conventions, and uploaded them to the FAIR-adhering magnetic data repository, earthref.org/MagIC. The reinterpreted site-level results from the three laboratories are mutually consistent, permitting the individual data sets to be combined and analyzed as single regional entities. Through incorporation into the MagIC repository, these legacy data are now accessible for incorporation into archaeomagnetic and global magnetic field modeling efforts, critical to understanding Earth\u27s magnetic field variation through time. In the Four Corners region of the United States Southwest, this digitized archive advances the development of a new regional paleosecular variation curve used in archaeomagnetic dating. This project highlights both the value and complexities of managing legacy data; the many lessons learned to set a precedent for future paleomagnetic data recovery efforts