The Distribution and Biogenic Origins of Zinc in the Mineralised Tooth Tissues of Modern and Fossil Hominoids: Implications for Life History, Diet and Taphonomy.

Zinc is incorporated into enamel, dentine and cementum during tooth growth. This work aimed to distinguish between the processes underlying Zn incorporation and Zn distribution. These include different mineralisation processes, the physiological events around birth, Zn ingestion with diet, exposure to the oral environment during life and diagenetic changes to fossil teeth post-mortem. Synchrotron X-ray Fluorescence (SXRF) was used to map zinc distribution across longitudinal polished ground sections of both deciduous and permanent modern human, great ape and fossil hominoid teeth. Higher resolution fluorescence intensity maps were used to image Zn in surface enamel, secondary dentine and cementum, and at the neonatal line (NNL) and enamel-dentine-junction (EDJ) in deciduous teeth. Secondary dentine was consistently Zn-rich, but the highest concentrations of Zn (range 197-1743 ppm) were found in cuspal, mid-lateral and cervical surface enamel and were similar in unerupted teeth never exposed to the oral environment. Zinc was identified at the NNL and EDJ in both modern and fossil deciduous teeth. In fossil specimens, diagenetic changes were identified in various trace element distributions but only demineralisation appeared to markedly alter Zn distribution. Zinc appears to be tenacious and stable in fossil tooth tissues, especially in enamel, over millions of years.

Using SXRF and LA-ICP-TOFMS to Explore Evidence of Treatment and Physiological Responses to Leprosy in Medieval Denmark.

Leprosy can lead to blood depletion in Zn, Ca, Mg, and Fe and blood enrichment in Cu. In late medieval Europe, minerals were used to treat leprosy. Here, physiological responses to leprosy and possible evidence of treatment are investigated in enamel, dentine, and cementum of leprosy sufferers from medieval Denmark (n = 12) and early 20th century Romania (n = 2). Using SXRF and LA-ICP-TOFMS, 12 elements were mapped in 15 tooth thin sections, and the statistical covariation of paired elements was computed to assess their biological relevance. The results show marked covariations in the Zn, Ca, and Mg distributions, which are compatible with clinical studies but cannot be directly attributed to leprosy. Minerals used historically as a treatment for leprosy show no detectable intake (As, Hg) or a diffuse distribution (Pb) related to daily ingestion. Intense Pb enrichments indicate acute incorporations of Pb, potentially through the administration of Pb-enriched medication or the mobilization of Pb from bone stores to the bloodstream during intense physiological stress related to leprosy. However, comparisons with a healthy control group are needed to ascertain these interpretations. The positive correlations and the patterns observed between Pb and essential elements may indicate underlying pathophysiological conditions, demonstrating the potential of SXRF and LA-ICP-TOFMS for paleopathological investigations.

Impact of claudin-10 deficiency on amelogenesis: Lesson from a HELIX tooth.

In epithelia, claudin proteins are important components of the tight junctions as they determine the permeability and specificity to ions of the paracellular pathway. Mutations in CLDN10 cause the rare autosomal recessive HELIX syndrome (Hypohidrosis, Electrolyte imbalance, Lacrimal gland dysfunction, Ichthyosis, and Xerostomia), in which patients display severe enamel wear. Here, we assess whether this enamel wear is caused by an innate fragility directly related to claudin-10 deficiency in addition to xerostomia. A third molar collected from a female HELIX patient was analyzed by a combination of microanatomical and physicochemical approaches (i.e., electron microscopy, elemental mapping, Raman microspectroscopy, and synchrotron-based X-ray fluorescence). The enamel morphology, formation time, organization, and microstructure appeared to be within the natural variability. However, we identified accentuated strontium variations within the HELIX enamel, with alternating enrichments and depletions following the direction of the periodical striae of Retzius. These markings were also present in dentin. These data suggest that the enamel wear associated with HELIX may not be related to a disruption of enamel microstructure but rather to xerostomia. However, the occurrence of events of strontium variations within dental tissues might indicate repeated episodes of worsening of the renal dysfunction that may require further investigations.

Native Separation and Metallation Analysis of SOD1 Protein from the Human Central Nervous System: a Methodological Workflow.

Studies of the metal content of metalloproteins in tissues from the human central nervous system (CNS) can be compromised by preparative techniques which alter levels of, or interactions between, metals and the protein of interest within a complex mixture. We developed a methodological workflow combining size exclusion chromatography, native isoelectric focusing, and either proton or synchrotron X-ray fluorescence within electrophoresis gels to analyze the endogenous metal content of copper-zinc superoxide dismutase (SOD1) purified from minimal amounts (<20 mg) of post-mortem human brain and spinal cord tissue. Abnormal metallation and aggregation of SOD1 are suspected to play a role in amyotrophic lateral sclerosis and Parkinson's disease, but data describing SOD1 metal occupancy in human tissues have not previously been reported. Validating our novel approach, we demonstrated step-by-step metal preservation, preserved SOD1 activity, and substantial enrichment of SOD1 protein versus confounding metalloproteins. We analyzed tissues from nine healthy individuals and five CNS regions (occipital cortex, substantia nigra, locus coeruleus, dorsal spinal cord, and ventral spinal cord). We found that Cu and Zn were bound to SOD1 in a ratio of 1.12 ± 0.28, a ratio very close to the expected value of 1. Our methodological workflow can be applied to the study of endogenous native SOD1 in a pathological context and adapted to a range of metalloproteins from human tissues and other sources.

Globally distributed iridium layer preserved within the Chicxulub impact structure.

The Cretaceous-Paleogene (K-Pg) mass extinction is marked globally by elevated concentrations of iridium, emplaced by a hypervelocity impact event 66 million years ago. Here, we report new data from four independent laboratories that reveal a positive iridium anomaly within the peak-ring sequence of the Chicxulub impact structure, in drill core recovered by IODP-ICDP Expedition 364. The highest concentration of ultrafine meteoritic matter occurs in the post-impact sediments that cover the crater peak ring, just below the lowermost Danian pelagic limestone. Within years to decades after the impact event, this part of the Chicxulub impact basin returned to a relatively low-energy depositional environment, recording in unprecedented detail the recovery of life during the succeeding millennia. The iridium layer provides a key temporal horizon precisely linking Chicxulub to K-Pg boundary sections worldwide.

Synchrotron X-ray fluorescence imaging of strontium incorporated into the enamel and dentine of wild-shot orangutan canine teeth.

OBJECTIVES: Dental hard tissues contain trace elements of both dietary and environmental origin. One objective was to demonstrate that a longitudinal record of synchronous Sr incorporation into enamel and dentine can be retrieved from museum specimens of once-free-living endangered species. Further objectives were to quantify sudden fluctuations in Sr concentration and estimate the extent of Sr overprinting back into dentine and enamel formed prior to the time of Sr ingestion. MATERIALS AND METHODS: Daily incremental markings were used to determine rates and times of tooth formation and synchrotron X-ray fluorescence of the same polished ground sections to image Sr distribution in a male and a female orangutan canine. The X-ray beam was monochromatised to 17.0 keV and focused to 500 × 500 nm2. Scans were performed at either 25.0 or 5.0 µm resolution. RESULTS: Baseline Sr levels ranged between 215-750 ppm. Multiple short, intense Sr labels reaching 750- 1,625 ppm occurred randomly throughout 15-22 years of tooth formation. In dentine, Sr concentration increased gradually away from the EDJ, while in enamel, it reduced towards the enamel surface. Using daily incremental markings, Sr overprinting into earlier formed dentine and enamel was estimated to be ∼12-45 days. There was no evidence of Sr overprinting by maturational ameloblasts. CONCLUSIONS: A good record of growth and trace element incorporation into tooth tissues can be retrieved from museum specimens. Short, intense Sr labels were equally well time-resolved in enamel and dentine and could be distinguished from more diffuse background levels. Enamel maturation appears to have no quantifiable effect.

Sub-micrometer Nanosecond LA-ICP-MS Imaging at Pixel Acquisition Rates above 250 Hz via a Low-Dispersion Setup.

The analytical figures of merit of a low-dispersion (ultrafast) ablation cell geometry within the Cobalt ablation chamber, integrated into a nanosecond laser ablation-inductively coupled plasma-mass spectrometer system, are reported. The system was investigated for its capability for fast high-resolution elemental imaging. A spot of 0.6 µm diameter was achieved on the sample surface by aperture imaging of a 10 µm pinhole. The resulting conical crater (0.6 µm ⌀ × 130 nm↓) morphology in a Au-coated glass target and carbon-coated silica wafer was characterized with atomic force microscopy. The Cobalt ablation chamber is based around a motorized height-adjustable tube cell, which allows modulating the sampling distance, i.e. the distance between the sample surface and the cell inlet, in a dynamic manner. This distance was observed to influence the single pulse response profile. The variation of the average signal intensity at multiple sample heights within a range of 0.5 mm was <3% RSD. Under optimum conditions, single pulse responses with a full width at 10% of the maximum peak intensity (FW0.1M) of ∼1 ms can be achieved for 238U upon ablation of NIST SRM612 glass, effectively opening the way to pixel acquisition rates up to 1 kHz. To demonstrate the potential of this technology, the elemental distribution of Zn in small intestine villi of mice subjected to a Zn-enriched diet was imaged using the 0.6 µm spot size, and rapid imaging of a zircon grain cross-section was performed.

High-resolution imaging and single-cell analysis via laser ablation-inductively coupled plasma-mass spectrometry for the determination of membranous receptor expression levels in breast cancer cell lines using receptor-specific hybrid tracers.

This work evaluates the possibility of placement of high-resolution imaging and single-cell analysis via laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) within precision medicine by assessing the suitability of LA-ICP-MS as a micro-analytical technique for the localization and quantification of membranous receptors in heterogeneous cell samples that express both the membrane-bound receptors C-X-C chemokine receptor type 4 (CXCR4) and epidermal growth factor receptor (EGFR). Staining of the breast cancer cell lines MDA-MB-231 X4 and MDA-MB-468 was achieved using receptor-specific hybrid tracers, containing both a fluorophore and a DTPA single-lanthanide chelate. Prior to LA-ICP-MS imaging, fluorescence confocal microscopy (FCM) imaging was performed to localize the receptors, hereby enabling direct comparison. Based on the different expression levels of CXCR4 and EGFR, a distinction could be made between the cell lines using both imaging modalities. Furthermore, FCM and LA-ICP-MS demonstrated complementary characteristics, as a more distinct discrimination could be made between both cell lines based on the EGFR-targeting hybrid tracer via LA-ICP-MS, due to the intrinsic CXCR4-related green fluorescent protein (GFP) signal present in the MDA-MB-231 X4 cells. Employing state-of-the-art LA-ICP-MS instrumentation in bidirectional area scanning mode for sub-cellular imaging of MDA-MB-231 X4 cells enabled the specific binding of the CXCR4-targeting hybrid tracer to the cell membrane to be clearly demonstrated. The stretching of cells over the glass substrate led to a considerably higher signal response for pixels at the cell edges, relative to the more central pixels. The determination of the expression levels of CXCR4 and EGFR for the MDA-MB-468 cell line was performed using LA-ICP-MS single-cell analysis (sc-LA-ICP-MS) and external calibration, based on the quantitative ablation of Ho-spiked dried gelatin droplet standards. Additionally, a second calibration approach was applied based on spot ablation of highly homogeneous dried gelatin gels in combination with the determination of the ablated volume using atomic force microscopy (AFM) and yielded results which were in good agreement with the expression levels determined via flow cytometry (FC) and mass cytometry (MC). Hybrid tracers enable a direct comparison between (i) FCM and LA-ICP-MS imaging for the evaluation of the microscopic binding pattern and between (ii) FC, MC and sc-LA-ICP-MS for the quantification of receptor expression levels in single cells.

Laser Ablation-Inductively Coupled Plasma Time-of-Flight Mass Spectrometry Imaging of Trace Elements at the Single-Cell Level for Clinical Practice.

In this work, a combination of routine clinical practice and state-of-the-art laser ablation-inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOFMS) imaging is presented for multielement analysis of single cells on clinical samples. More specifically, routinely drawn blood thin films of a patient undergoing treatment with the anticancer drug cisplatin were studied. The presented label-free approach enabled rapid analysis of hundreds of cells at the single-cell level within a few minutes without additional tailored sample preparation. The employed low-dispersion LA setup is based on the tube-type COBALT ablation cell in combination with the aerosol rapid introduction system (ARIS) providing pixel-resolved imaging at 250-500 Hz for biological sample material. In order to cope with the short transient signals of only a few milliseconds delivered by the laser ablation setup, an icpTOF 2R TOF-based ICP-MS instrument was used for analysis, which has a mass coverage of m/ z = 14-256. Leukocytes and erythrocytes, imaged with a laser beam of 4 µm and pixel interspacing of 2 µm, were differentiated on the basis of their intrinsic trace-elemental pattern. Overall, red blood cells displayed high iron intensities, whereas individual white blood cells were characterized by their high phosphorus content and increased sulfur signal. Unsupervised multivariate statistical analysis was applied to the data set. Principal component plots showed a clear clustering of leukocytes versus erythrocytes. The approach allowed studying not only the drug distribution between plasma and cells but also, for the first time, the preferential accumulation of platinum in different blood cell types without the need of cell fixation and labeling. Extracellular hotspots of platinum were observed, whereas only a small fraction of platinum was associated with erythrocytes. The investigation demonstrates the potential of low-dispersion LA-ICP-TOFMS as a rapid and powerful tool for label-free single-cell imaging in the clinical context.

Correction to: Three-dimensional reconstruction of the distribution of elemental tags in single cells using laser ablation ICP-mass spectrometry via registration approaches.

The authors would like to call the reader's attention to the fact that unfortunately the originally provided affiliation for Dr. Tomoko Asaoka was not correct.