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1. Evaluating methods for determining mercury concentrations in ancient marine fish and mammal bones as an approach to assessing millennial-scale fluctuations in marine ecosystems

   https://doi.org/10.3389/fevo.2023.1251282  

   Avery, Julie P.; Castellini, J. Margaret; Misarti, Nicole; Keenan, Mary; Gastaldi, Angela; Funk, Caroline; O’Hara, Todd M.; Rea, Lorrie D. (October 2023, Frontiers in Ecology and Evolution)

   Parducci, Laura (Ed.)

   Millennial-scale datasets of heavy metals in biota are difficult to obtain but are important for determining patterns and underlying drivers of toxicant concentrations. This is particularly important to better discriminate contemporary natural and anthropogenic sources. Globally mercury is a contaminant of concern. Post-industrial increases in mercury in arctic biota have been documented and monitoring of Steller sea lions (Eumetopias jubatus) in the Aleutian Islands, Alaska, has revealed a high proportion of pups with fur mercury concentrations above thresholds of concern in some regions. As bone is a tissue that is well preserved in archeological middens, it may prove useful for developing long-term mercury data sets under appropriate conditions. The goal of this study was to evaluate methodologies for measuring mercury concentration in Steller sea lion bone using a direct mercury analyzer, considering sample preparation methods and variability among bone tissue types (e.g., compact versus spongy bone). Finally, we directly compare sensitivity and precision of two different direct mercury analyzer models. Based on the methods presented here, direct mercury analysis using the Nippon MA-3000 can quantify small (ppb) quantities of Hg accurately and precisely in 20 to 60mg of bone with minimal specimen processing. The described method is efficient, relatively inexpensive, and requires minimal bone, conserving rare and valuable specimens. Hydrogen peroxide cleaning and collagen extraction were not required, and may be detrimental for optimal Hg quantification in bone. Further, while homogenization of distinct compact and spongy bone did not impact concentration determination, variance of technical replicates was lower improving quantitation precision. Most importantly, significant differences between compact and spongy bone exist within some individual specimen; however, the difference is not consistent and may indicate differential Hg exposure windows influenced by turnover rate of bone types. We conclude bone provides a natural archive for mercury ecosystem dynamics over millennial time scales in regions where appropriate samples are available. Compact bone has lower and less variable [THg] simplifying analysis and interpretation of data; however, the more dynamic concentrations observed in spongy bone should not be dismissed as invaluable due to their variability in [THg]. Comparisons of [THg] between bone type within individual may provide insight into more acute changes in mercury exposure within an individual’s lifetime. 

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2. Characterization of collagen formation surrounding osteocytes using second and third harmonic generation

   https://doi.org/10.1117/12.2510814  

   Pendleton, Emily G.; Tehrani, Kayvan F.; Barrow, Ruth P.; Mortensen, Luke J. (February 2019, Proc. SPIE 10871, Multimodal Biomedical Imaging XIV)

   More than 54 million Americans have or are at high risk of developing a metabolic bone disease; disorders of bone strength that leave individuals with fragile bones and disabilities. The gold standard to evaluate these diseases is dual energy x-ray absorptiometry, but this only measures mineral content. These diseases, however, impact collagen and mineral integrity which impede the bone’s ability to store hormones, proteoglycans, and glycoproteins imperative to homeostasis. We have established a second harmonic generation (SHG) polarimetric assay that describes bone collagen organization. To further our analysis, we propose multimodal optical evaluation of bone quality with third harmonic generation (THG) to measure osteocyte dendritic processes. This method of analysis could be used to evaluate the disease state of bone and response to therapy. 

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3. The Cortical Bone Metabolome of C57BL / 6J Mice Is Sexually Dimorphic

   https://doi.org/10.1002/jbm4.10654  

   Welhaven, Hope D.; Vahidi, Ghazal; Walk, Seth T.; Bothner, Brian; Martin, Stephen A.; Heveran, Chelsea M.; June, Ronald K. (June 2022, JBMR Plus)

   ABSTRACT Cortical bone quality, which is sexually dimorphic, depends on bone turnover and therefore on the activities of remodeling bone cells. However, sex differences in cortical bone metabolism are not yet defined. Adding to the uncertainty about cortical bone metabolism, the metabolomes of whole bone, isolated cortical bone without marrow, and bone marrow have not been compared. We hypothesized that the metabolome of isolated cortical bone would be distinct from that of bone marrow and would reveal sex differences. Metabolite profiles from liquid chromatography–mass spectrometry (LC‐MS) of whole bone, isolated cortical bone, and bone marrow were generated from humeri from 20‐week‐old female C57Bl/6J mice. The cortical bone metabolomes were then compared for 20‐week‐old female and male C57Bl/6J mice. Femurs from male and female mice were evaluated for flexural material properties and were then categorized into bone strength groups. The metabolome of isolated cortical bone was distinct from both whole bone and bone marrow. We also found sex differences in the isolated cortical bone metabolome. Based on metabolite pathway analysis, females had higher lipid metabolism, and males had higher amino acid metabolism. High‐strength bones, regardless of sex, had greater tryptophan and purine metabolism. For males, high‐strength bones had upregulated nucleotide metabolism, whereas lower‐strength bones had greater pentose phosphate pathway metabolism. Because the higher‐strength groups (females compared with males, high‐strength males compared with lower‐strength males) had higher serum type I collagen cross‐linked C‐telopeptide (CTX1)/procollagen type 1 N propeptide (P1NP), we estimate that the metabolomic signature of bone strength in our study at least partially reflects differences in bone turnover. These data provide novel insight into bone bioenergetics and the sexual dimorphic nature of bone material properties in C57Bl/6 mice. © 2022 The Authors.JBMR Pluspublished by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research. 

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4. Diet shifts drive mercury bioaccumulation and distribution in tissues of the longnose lancetfish (Alepisaurus ferox)

   https://doi.org/10.1016/j.marpolbul.2025.117590  

   Chen, Rachel S; Paulson, Erik T; Schartup, Amina T; Choy, C Anela (April 2025, Marine Pollution Bulletin)

   Monitoring the impacts of global efforts to reduce mercury (Hg) emissions is limited by the collection of biological samples at appropriate spatiotemporal scales. This is especially true in the deep sea, a vast region with food webs that cycle bioaccumulative methylmercury (MeHg). Within a species, understanding the distribution of Hg across tissue types can reveal how Hg accumulates in the body and inform how useful a species is for biomonitoring geographic regions or vertical habitats of the ocean. We focus on a globally distributed deep-sea fish, the longnose lancetfish (Alepisaurus ferox, n = 69 individuals), and measure total mercury (THg) and MeHg concentrations in 10 tissue types (brain, caudal white muscle, dorsal white muscle, gallbladder, gill filament, gonad, heart, intestine, liver, and stomach lining). Across all tissue types, THg and MeHg concentrations were higher in large lancetfish (≥1.8 kg) than small lancetfish (<1.8 kg), but concentrations were relatively stable within size classes. THg levels were highest in liver, intestine, and heart, followed by caudal white muscle, dorsal white muscle, stomach lining, and gill filament, then by gonad and gallbladder. We describe how ontogenetic diet shifts explain Hg bioaccumulation in pelagic predators inhabiting similar waters to lancetfish. We hypothesize that diet shifts to deeper-dwelling prey and fishes drive increases in THg and MeHg concentrations in large lancetfish. We propose lancetfish as a strong candidate for monitoring spatiotemporal variability of Hg in the deep pelagic – they are commonly captured in global fisheries and may reflect Hg sources in two distinct vertical habitats of the ocean. 

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5. The Tiny Skull of the Peruvian Gecko Pseudogonatodes barbouri (Gekkota: Sphaerodactylidae) Obtained via a Divide-And-Conquer Approach to Morphological Data Acquisition

   https://doi.org/10.2994/SAJH-D-17-00113.1  

   Bauer, Aaron M.; Beach-Mehrotra, Mallika; Bermudez, Yarima; Clark, Geneva E.; Daza, Juan D.; Glynne, Elizabeth; Hagyari, David; Harnden, Jennifer M.; Holovacs, Nicholas; Kanasiro, Andre; et al (August 2018, South American Journal of Herpetology)

   The Peruvian sphaerodactyl gecko, Pseudogonatodes barbouri, is among the smallest reptile species in South America. Morphological information about this species, or even the genus, is limited. In this study, we produced a bone-by-bone description from the skull and atlantoaxial complex to contribute new phenotypic information about this poorly known lizard. To achieve this objective, we employed a divide-and-conquer approach in which each author digitally isolated one or two bones from the skull and produced a written description of these elements, thereby reducing 3D imaging processing and description to a fraction of time. In addition to a reduced phalanx in the fourth toe of both the hand and foot, the genus is characterized by having nasal bones with a broad lateral wing, an ectopterygoid that clasps the pterygoid, and an anterior shifting of the paroccipital process and as consequence the position of the quadrate, and squamosal not participating in the quadrate suspension. There are also modifications in fenestration and foramina and a trend towards synostosis of the jaw bones (e.g., coronoid + splenial, compound bone + surangular). Pseudogonatodes bears four long processes on the intercentrum of the axis; which is a character of New World sphaerodactyls. 

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