Immobilized Bisphosphonates as Potential Inhibitors of Bioprosthetic Calcification: Effects on Various Xenogeneic Cardiovascular Tissues

Calcification is the major factor limiting the clinical use of bioprostheses. It may be prevented by the immobilization of bisphosphonic compounds (BPs) on the biomaterial. In this study, we assessed the accumulation and structure of calcium phosphate deposits in collagen-rich bovine pericardium (Pe) and elastin-rich porcine aortic wall (Ao) and bovine jugular vein wall (Ve) cross-linked with glutaraldehyde (GA) or diepoxy compound (DE). These tissues were then modified with pamidronic (PAM) acid or 2-(2′-carboxyethylamino)ethylidene-1,1-bisphosphonic (CEABA) acid. Tissue transformations were studied using Fourier-transform infrared spectroscopy. After subcutaneous implantation of the biomaterials in 220 rats, calcification dynamics were examined using atomic absorption spectrophotometry, light microscopy after von Kossa staining, and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy The calcium content in all GA-cross-linked tissues and DE-cross-linked Ao increased to 100–160 mg/g on day 60 after implantation. BPs prevented the accumulation of phosphates on the surface of all materials and most effectively inhibited calcification in GA-cross-linked Ao and DE-cross-linked Pe. PAM containing -OH in the R1 group was more effective than CEABA containing -H in R1. The calcification-inhibitory effect of BPs may be realized through their ability to block nucleation and prevent the growth of hydroxyapatite crystals.

New Middle Eocene proboscidean from Togo illuminates the early evolution of the elephantiform-like dental pattern

Africa has played a pivotal role in the evolution of early proboscideans (elephants and their extinct relatives), yet vast temporal and geographical zones remain uncharted on the continent. A long hiatus encompassing most of the Eocene (Ypresian to the Early Priabonian, around 13 Myr timespan) considerably hampers our understanding of the early evolutionary history of the group. It is notably the case with the origin of its most successful members, the Elephantiformes, i.e. all elephant-like proboscideans most closely related to modern elephants. Here, we describe a proboscidean lower molar discovered in Lutetian phosphate deposits from Togo, and name a new genus and species, Dagbatitherium tassyi . We show that Dagbatitherium displays several elephantiform dental characteristics such as a three-layered Schmelzmuster, the presence of a mesoconid, transversely enlarged buccal cusps and the individualization of a third lophid closely appressed to a minute distal cingulid. Dagbatitherium represents a stem Elephantiformes, pushing back the origin of the group by about 10 Myr, i.e. a third of its currently known evolutionary history. More importantly, Dagbatitherium potentially unlocks the puzzle of the origin of the unique elephantiform tooth crown organization by bridging a critical temporal and morphological gap between early bunodont incipiently bilophodont proboscidean taxa and more derived elephantiforms.

Stratigraphy of the Khuvsgul Group, Mongolia

The Khuvsgul Group (Khuvsgul Province, Mongolia) is a Late Neoproterozoic to Cambrian carbonate-dominated succession that includes minor glacial diamictite and one of the largest known ore-grade phosphate deposits in the world. These strata, which have experienced low-grade metamorphism, are exposed in the Khoridol-Saridag Range on the western margin of Lake Khuvsgul. Since 2017, new geologic mapping and field studies have been conducted in the Khuvsgul region. During the course of this work, it has become necessary to restructure the stratigraphic framework of the Khuvsgul Group in order to better facilitate geologic mapping, stratigraphic observations, and regional correlations. We have divided the lower Khuvsgul Group into four distinct formations spanning the Cryogenian and Ediacaran, each of which encompass strata associated with the Sturtian glaciation, Cryogenian non-glacial interlude, Marinoan glaciation, and basal Ediacaran transgression respectively. The phosphorites of the Khuvsgul Group are now included within a new distinct formation, while the overlying Cambrian carbonates and siliciclastic rocks have been further subdivided to streamline mapping and correlation efforts. The stratigraphic framework outlined below will simplify identification and differentiation of Khuvsgul Group rocks in the field and provide a foundation for the interpretation of Khuvsgul Group strata within the context of the changing climatic, tectonic, and paleoenvironmental conditions of the late Neoproterozoic and early Cambrian.

Investigation on physicochemical properties of graphene oxide/nano-hydroxyapatite composites and its biomedical applications

Graphene oxide/nano-hydroxyapatite (GO/nHAP) composites were synthesized by simultaneous titration method. The GO powder was uniformly dispersed ultrasonically in a solution containing Ca(NO3)2. It was co-titrated with (NH4)2HPO4, during which NH3·H2O was used to maintain pH of about 10. Transmission electron microscopy (TEM) showed that HAP had a drusy acicular crystal structure with 100–200 nm length in the composite. The Ca2+ ions were attracted by the negatively charged oxygen functional groups present on GO sheets. They also oriented the growth of hydroxyapatite preferentially along (112) plane, which was also consistent with X-ray diffractometry (XRD) results. According to X-ray photoelectron spectroscopic (XPS) results, the peak intensities of the C–O and C–C groups increased in the GO/nHAP composite. However, the number of –COO– and C–O–C groups was reduced as well as the position of peaks shifted due to electrostatic interactions. These results were also corroborated with Fourier transform infrared spectroscopy (FTIR). MTT assay indicated that GO/nHAP composites had a significant effect on proliferation of 293T cells and good biomimetic mineralization as shown by in vitro bioactivity assays. EDS spectroscopy confirmed that the Ca/P ratio in calcium phosphate deposits was 1.62, which was close to the ratio of 1.64 in natural bone. The biological performance of GO/nHAP composite proved it to be a promising candidate for bone regeneration and implantation.

An unnoticed reason of renal failure: Acute phosphate nephropathy

Acute Phosphate Nephropathy is a clinical and pathological finding characterized by acute and subsequent chronic renal failure following the use of intestinal cleansers containing sodium phosphate. The pathophysiology of Acute Phosphate Nephropathy occurs due to the increase of sodium and water absorption in the proximal tubules due to hypovolemia, and the accumulation of calcium phosphate load in the distal tubules in the collector and distal canals. Renal biopsy findings include acute and chronic tubular damage with tubular and interstitial calcium phosphate deposits. Prevention of Acute Phosphate Nephropathy can be achieved by hydration before and after the use of calcium phosphate in risky patients, minimizing the sodium phosphate dose, and having 12-hour intervals between sodium phosphate applications. In this article, we aimed to present the patients who used sodium phosphate for colonoscopy and developed Acute Phosphate Nephropathy.

Geophysical Prospecting for Groundwater Resources in Phosphate Deposits (Morocco)

The Moroccan phosphate deposits are the largest in the world. Phosphatic layers are extracted in open-pit mines mainly in the sedimentary basins of Gantour and Ouled Abdoun in Central Morocco. The purpose of this study was to prospect and evaluate the water potential of aquifers incorporated in the phosphatic series using the following geophysical methods: Magnetic resonance sounding (MRS), electrical resistivity tomography (ERT), time-domain electromagnetics (TDEM), and frequency-domain electromagnetics (FDEM). The objective was, on the one hand, to contribute to the success of the drinking water supply program in rural areas around mining sites, and on the other hand, to delimit flooded layers in the phosphatic series to predict the necessary mining design for their extraction. The use of geophysical methods made it possible to stratigraphically locate the most important aquifers of the phosphatic series. Their hydraulic parameters can be evaluated using the MRS method while the mapping of their recharge areas is possible through FDEM surveys. The results obtained in two selected experimental zones in the mining sites of Youssoufia and Khouribga are discussed in this paper. The application of the implemented approach to large phosphate mines is in progress in partnership with the mining industry.