Vincent Balter

Dinosaur annual movement patterns are difficult to determine and have primarily been inferred from bulk Sr isotope analyses of tooth enamel, which provide a limited monthly temporal resolution only. We incrementally measured the phosphate oxygen isotope composition (δ18Op) and strontium isotope ratio of bioapatite (87Sr/86Sr) from long bones of the ornithischian dinosaur Maiasaura peeblesorum to reconstruct temporal changes of the hydrogeological environment and investigate intra- and pluri-annual movements. The analyses were performed on the mid-diaphyseal tibial cortex of three individuals representing different ontogenetic stages (small juvenile, large juvenile, and subadult). First, we performed synchrotron X-ray fluorescence (µXRF) chemical mapping of the mid-diaphyseal tibial cortex to assess Sr preservation based on the spatial distribution of Ca, Sr, U, and Y. The Y-enriched periosteal surfaces exhibited an elemental distribution consistent with diagenetic alteration. Deep into the cortical surface, the distribution of Sr similar to what is observed in modern vertebrates, the low concentrations of diagenetic elements, and the absence of a relationship between Sr concentration and 87Sr/86Sr support the preservervation of biogenic Sr isotope compositions. Sr isotope compositions showed limited variation within individuals, suggesting that the three individuals grew and died within the same hydrogeological region. The limited variations are interpreted as reflecting short-distance movements related to resource availability. We propose that the movement and sedentary patterns of Maiasaura were linked to its breeding strategy, with periods of site fidelity associated with egg incubation and parental care, followed by movements that allowed the regeneration of primary producers at nesting sites.

Ca isotopes are measured on a Neoma MC-ICP-MS/MS with H ₂ or SF ₆ , with the latter configuration showing outstanding immunity of the ⁴² CaF/ ⁴⁰ CaF ratio to matrix effects.

This study focuses on the development of a method for the precise isotopic analysis of potassium, magnesium, and calcium from a single sample aliquot of biological material.

Radiogenic strontium isotopes (⁸⁷Sr/⁸⁶Sr) and the alkaline earth ratios (AERs) Sr/Ca and Ba/Ca in fossil dental enamel can inform the habitat, residence and life histories of early hominins recovered from the Pleistocene cradle-of-humankind sites of Gauteng, South Africa. Key questions, which may be addressed with these indices, are the relative exploitation of wet versus dry botanic regimes and whether early hominins dispersed in a manner similar to that of chimpanzees (characterized by male philopatry and female dispersal at puberty) or to that of humans (who are not so characterized). Here we developed 28 new dental chronologies in 20 Paranthropus robustus teeth from Swartkrans and Kromdraai. Resulting geochemical time series demonstrate that, while maternal ⁸⁷Sr/⁸⁶Sr in earlier-forming teeth varies widely, third molar ⁸⁷Sr/⁸⁶Sr, derived from postweaning solid foods, progressively converges to 0.7306 ± 0.0035 (± 2 s.d.), which we express as the local isotopically delineated exploitation area (LIDEA). The spatial resolution of LIDEA is determined using a bioavailable ⁸⁷Sr/⁸⁶Sr isoscape. In this environmental context, we interpret LIDEA as a quantifiable signal indicating eurytopy (generalization), with some 30% of Sr deriving from riparian woodland habitats. With regard to residence, many individuals arrived at the site after second molar mineralization, while some matured locally, demonstrating both male and female dispersal as well as lifelong local residence. Analysis of both ⁸⁷Sr/⁸⁶Sr and the AERs further highlights concomitant patterns, as well as numerous periodicities that may be related to resource depletion, seasonality or lunar cycles.

Balanced mTOR activity and iron levels are crucial for muscle integrity, with evidence suggesting mTOR regulates cellular iron homeostasis. In this study, we investigated iron metabolism in muscle-specific mTOR knockout mice (mTORmKO) and its relation to their myopathy. The mTORmKO mice exhibited distinct iron content patterns across muscle types and ages. Slow-twitch soleus muscles initially showed reduced iron levels in young mice, which increased with the dystrophy progression but remained within control ranges. In contrast, the less affected fast-twitch muscles maintained near-normal iron levels from a young age. Interestingly, both mTORmKO muscle types exhibited iron metabolism markers indicative of iron excess, including decreased transferrin receptor 1 (TFR1) and increased levels of ferritin (FTL) and ferroportin (FPN) proteins. Paradoxically, these changes were accompanied by downregulated Ftl and Fpn mRNA levels, indicating post-transcriptional regulation. This discordant regulation resulted from disruption of key iron metabolism pathways, including NRF2/NFE2L2, HIFs, and AKT/PKB signaling. Mechanistically, mTOR deficiency impaired transcriptional regulation of iron-related genes mediated by NRF2 and HIFs. Furthermore, it triggered ferritin accumulation through two NRF2 mechanisms: (1) derepression of ferritin translation via suppression of the FBXL5-IRP axis, and (2) autophagosomal sequestration driven by NCOA4-dependent ferritin targeting to autophagosomes, coupled with age-related impairments of autophagy linked to chronic AKT/PKB activation. Three-week spermidine supplementation in older mTORmKO mice was associated with normalized AKT/PKB-FOXO signaling, increased endolysosomal FTL and reduced total FTL levels in the dystrophic soleus muscle. These findings underscore mTOR’s crucial role in skeletal muscle iron metabolism and suggest spermidine as a potential strategy to address impaired ferritinophagy due to autophagy blockade in dystrophic muscle.

La diversité génétique et culturelle des sociétés contemporaines des populations du Pacifique sud résulte de contacts incessants entre les îles depuis 3000 ans, de la colonisation par les Lapita jusqu’à la colonisation européenne il y a 400-300 ans. Dans cette vaste région, le projet BIFO s’intéresse à une zone d’étude circonscrite au sud et au centre du Vanuatu, marquée par des relations avec la Polynésie au début du IIe millénaire et l’arrivée d’Européens au XVIIIe s. Ce projet vise à carac...

Correction for ‘(LA)-MC-ICPMS/MS measurement of Sr radiogenic isotope ratios’ by Philippe Télouk et al., J. Anal. At. Spectrom., 2024, 39, 879–887.

Natural processes, from cosmochemistry to human homeostasis, can be traced by means of the mass-dependent fractionation of K isotopes because the ³⁹K/⁴¹K ratio is characterized by a wide range of variations (ca. 3‰). The measurement of the ³⁹K/⁴¹K ratio is traditionally achieved by multi-collector inductively coupled plasma mass spectrometers (MC-ICPMS), but is significantly impeded by large isobaric argide interferences on K isotopes. A new generation of MC-ICPMS equipped with a collision/reaction cell allows the quantitative elimination of argide interferences using H₂ as a reaction gas. We report on a set of high-precision K isotopic data obtained with the recently released ThermoScientific Neoma MC-ICPMS/MS equipped with a prefiltering system consisting of a double-Wien filter and a collision/reaction cell. In the low-resolution mode, the mass resolving power is ca. 2200, resulting in a K sensitivity of ca. 1000 V ppm⁻¹ for ³⁹K in dry mode with an Apex Omega desolvator. This large mass revolving power allows the observation of yet undetected interferences on the high-mass shoulders of ³⁹K and ⁴¹K. The interference is ca. 25 mV on ³⁹K and 1 mV on ⁴¹K in the low-resolution mode, similar in K and blank HNO₃ (0.05 M) solutions, increases when N₂ is added in the desolvator and decreases when He is added as a collision gas. The presence of these interferences, which contribute modestly < 0.02% of the K signal, is probably the result of the formation of complex organic compounds in the collision/reaction cell. However, blank subtraction is a critical step to achieve steady and accurate analysis of the ³⁹K/⁴¹K ratio. The overall stability of the analysis of the ³⁹K/⁴¹K ratio is greatly improved by using a continuous-flow microFAST Isotope autosampler. A survey on the potential effects of sample-standard mismatches reveals significant offsets for matrix elements (Ca, Mg and Na), no offset for acid molarity. Regarding the effect of sample-standard concentration mismatch, we show that the amplitude of the offset is session-dependent, such that no general correction could be applied. We use the autosampler adjustable injection flow rate to correct for a concentration mismatch up to ± 30% to recover expected K isotope composition within the ± 0.05‰ uncertainty. In these conditions, short-term external precision and long-term reproducibility are 0.07‰ (2SD, n = 500) and 0.08‰ (2SD, n = 66), respectively. For validation of the overall method, we finally purified K using a single step chemical separation by ion exchange chromatography, and measured the K isotope composition of geological and biological reference materials, for which we found values similar to the literature. Our study shows that the Neoma MC-ICPMS/MS with continuous flow injection is a robust instrumentation that will contribute to expediting high-precision K isotopic measurements for various applications.

Strontium isotopes with SF ₆ - and N ₂ O-based compounds in collision/reaction cell MC-ICPMS.