calcification process
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2021 ◽  
Vol 18 (22) ◽  
pp. 6061-6076
Author(s):  
Valentina Alice Bracchi ◽  
Giulia Piazza ◽  
Daniela Basso

Abstract. Recent advances on the mechanism and pattern of calcification in coralline algae led to contradictory conclusions. The evidence of a biologically controlled calcification process, resulting in distinctive patterns at the scale of family, was observed. However, the coralline calcification process has been also interpreted as biologically induced because of the dependency of its elemental composition on environmental variables. To clarify the matter, five collections of Lithothamnion corallioides from the Atlantic Ocean and the Mediterranean Sea, across a wide depth range (12–66 m), have been analyzed for morphology, anatomy and cell wall crystal patterns in both perithallial and epithallial cells to detect possible ultrastructural changes. L. corallioides shows the alternation of tiers of short-squared and long-ovoid/rectangular cells along the perithallus, forming a typical banding. The perithallial cell length decreases according to water depth and growth rate, whereas the diameter remains constant. Our observations confirm that both epithallial and perithallial cells show primary (PW) and secondary (SW) calcite walls. Rectangular tiles, with the long axis parallel to the cell membrane forming a multi-layered structure, characterize the PW. Flattened squared bricks characterize the SW, with roundish outlines enveloping the cell and showing a zigzag and cross orientation. Long and short cells have different thicknesses of PW and SW, increasing in short cells. Epithallial cells are one to three flared cells with the same shape of the PW and SW crystals. Despite the diverse seafloor environments and the variable L. corallioides growth rate, the cell walls maintain a consistent ultrastructural pattern with unaffected crystal shape and arrangement. A comparison with two congeneric species, L. minervae and L. valens, showed similar ultrastructural patterns in the SW but evident differences in the PW crystal shape. Our observations point to a biologically control rather than an induction of the calcification process in coralline algae and suggest a possible new morphological diagnostic tool for species identification, with relevant importance for paleontological applications. Finally, secondary calcite, in the form of dogtooth crystals that fill the cell lumen, has been observed. It represents a form of early alteration in living collections which can have implications in the reliability of climate and paleoclimate studies based on geochemical techniques.


2021 ◽  
Vol 22 (21) ◽  
pp. 11615
Author(s):  
Geoffrey Van den Bergh ◽  
Sofie De Moudt ◽  
Astrid Van den Branden ◽  
Ellen Neven ◽  
Hanne Leysen ◽  
...  

Arterial media calcification (AMC) is predominantly regulated by vascular smooth muscle cells (VSMCs), which transdifferentiate into pro-calcifying cells. In contrast, there is little evidence for endothelial cells playing a role in the disease. The current study investigates cellular functioning and molecular pathways underlying AMC, respectively by, an ex vivo isometric organ bath set-up to explore the interaction between VSMCs and ECs and quantitative proteomics followed by functional pathway interpretation. AMC development, which was induced in mice by dietary warfarin administration, was proved by positive Von Kossa staining and a significantly increased calcium content in the aorta compared to that of control mice. The ex vivo organ bath set-up showed calcified aortic segments to be significantly more sensitive to phenylephrine induced contraction, compared to control segments. This, together with the fact that calcified segments as compared to control segments, showed a significantly smaller contraction in the absence of extracellular calcium, argues for a reduced basal NO production in the calcified segments. Moreover, proteomic data revealed a reduced eNOS activation to be part of the vascular calcification process. In summary, this study identifies a poor endothelial function, next to classic pro-calcifying stimuli, as a possible initiator of arterial calcification.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Azumi Kuroyanagi ◽  
Takahiro Irie ◽  
Shunichi Kinoshita ◽  
Hodaka Kawahata ◽  
Atsushi Suzuki ◽  
...  

AbstractRapid increases in anthropogenic atmospheric CO2 partial pressure have led to a decrease in the pH of seawater. Calcifying organisms generally respond negatively to ocean acidification. Foraminifera are one of the major carbonate producers in the ocean; however, whether calcification reduction by ocean acidification affects either foraminiferal shell volume or density, or both, has yet to be investigated. In this study, we cultured asexually reproducing specimens of Amphisorus kudakajimensis, a dinoflagellate endosymbiont-bearing large benthic foraminifera (LBF), under different pH conditions (pH 7.7–8.3, NBS scale). The results suggest that changes in seawater pH would affect not only the quantity (i.e., shell volume) but also the quality (i.e., shell density) of foraminiferal calcification. We proposed that pH and temperature affect these growth parameters differently because (1) they have differences in the contribution to the calcification process (e.g., Ca2+-ATPase and Ω) and (2) pH mainly affects calcification and temperature mainly affects photosynthesis. Our findings also suggest that, under the IPCC RCP8.5 scenario, both ocean acidification and warming will have a significant impact on reef foraminiferal carbonate production by the end of this century, even in the tropics.


Author(s):  
Mirzaie Masoud ◽  
Josefina Kusnirova ◽  
Johann Philipp Addicks ◽  
Sheila Fatehpur

In vascular calcification, as a physiological process, intimal arterial calcification (IAC) associated with increased cardiovascular risk is distinguished from medial arterial calcification (MAC) localized mainly in the lamina elatica interna, which are not only based on different pathophysiological mechanisms. They also lead to different cardiovascular diseases. While intimal arterial calcification involves inflammation and lipid accumulation, a calcification process similar to desmal ossification plays the main role in medial arterial calcification. In this context, the phenotype change of smooth muscle cells from muscular type to synthesizing form in the tunica media is considered to be of great importance, which puts the matrix GLA protein, mainly involved in bone metabolism, in the center of interest. The present review work elucidates the molecular biological basis of interaction of matrix GLA protein subunits in the pathogenesis of vascular calcifications and the influence of diet on the consequences of underactivation of matrix GLA protein.


2021 ◽  
Author(s):  
Dorothee Kottmeier ◽  
Abdesslam Chrachri ◽  
Gerald Langer ◽  
Katherine Helliwell ◽  
Glen L Wheeler ◽  
...  

Coccolithophores produce the bulk of ocean biogenic calcium carbonate but this process is predicted to be negatively affected by future ocean acidification scenarios. Since coccolithophores calcify intracellularly, the mechanisms through which changes in seawater carbonate chemistry affect calcification remain unclear. Here we show that voltage-gated H+ channels in the plasma membrane of Coccolithus braarudii serve to regulate pH and maintain calcification under normal conditions, but have greatly reduced activity in cells acclimated to low pH. This disrupts intracellular pH homeostasis and impairs the ability of C. braarudii to remove H+ generated by the calcification process, leading to specific coccolith malformations. These coccolith malformations can be reproduced by pharmacological inhibition of H+ channels. Heavily-calcified coccolithophore species such as C. braarudii, which make the major contribution to carbonate export to the deep ocean, have a large intracellular H+ load and are likely to be most vulnerable to future decreases in ocean pH.


2021 ◽  
Author(s):  
Valentina Alice Bracchi ◽  
Giulia Piazza ◽  
Daniela Basso

Abstract. Recent advances on the mechanism and pattern of calcification in coralline algae lead to contradictory conclusions. Coralline calcification appears biologically induced, as suggested by the dependency of its elemental composition on environmental variables. However, evidence of a biologically controlled calcification process, resulting in distinctive patterns at the scale of family, was also observed. In order to clarify the matter, five collections of Lithothamnion corallioides from the Atlantic Ocean and the Mediterranean Sea, across a wide depth range (12–66 m) have been analyzed for morphology, anatomy and cell wall crystal patterns of both perithallial and epithallial cells, in order to detect possible ultrastructural changes. L. corallioides shows the alternation of tiers of short-squared and long-ovoid/rectangular cells along the perithallus, forming a typical banding. The perithallial cell length decreases according to water depth and growth-rate, whereas diameter remains constant. Our observations confirm that both epithallial and perithallial cells show primary (PW) and secondary (SW) calcite walls. Rectangular tiles, with the long axis parallel to the cell membrane forming a multi-layered structure, characterize the PW. Flattened squared bricks characterize the SW with roundish outlines enveloping the cell and showing a zigzag pattern. Long and short cells have different thickness of PW and SW, with a thicker SW and PW in short cells. Epithallial cells are one up to three flared cells, with the same shape of the PW and SW crystals. Despite the diverse seafloor environments and the variable L. corallioides growth-rate, the cell walls maintain a consistent ultrastructural pattern, with unaffected crystal shape and arrangement. A comparison with two congeneric species, L. minervae and L. valens, showed similar ultrastructural patterns in SW, but evident differences in the PW crystal shape. Our observations point to a biological control rather than an induction of the calcification process in coralline algae, and suggest a possible new morphological diagnostic tool for species identification, with relevant importance for paleontological application. Finally, secondary calcite, in form of dogtooth crystals that fill the cell lumen, has been observed. It represents a form of early diagenesis in living collections which can have implications in the reliability of climate and paleoclimate studies based on the geochemistry techniques.


2021 ◽  
Vol 39 (4) ◽  
pp. 202
Author(s):  
Ming-Hsiu Hsieh ◽  
Miki Izumi ◽  
Yukio Nakatani ◽  
Kuniaki Ohara

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Rolando A Cuevas ◽  
Luis HORTELLS ◽  
Camille Boufford ◽  
Cailyn Regan ◽  
Claire Chu ◽  
...  

Introduction: Calcific aortic valve disease (CAVD) is a disorder characterized by the slow, but a progressive thickening of the aortic valve leaflet that develops into severe calcification. The only current therapy is aortic valve replacement. Telomerase is an enzymatic complex best known for its telomere-extending activities on the ends of chromosomes yet, the catalytic subunit (TERT) has been implicated in multiple non-canonical transcriptional and epigenetic activities, including priming of mesenchymal stem cells (MSCs) to differentiate into osteoblasts, and transcriptional regulation of inflammatory genes. Hypothesis: We hypothesize that non-canonical TERT activity contributes to the progression of CAVD. Methods: We performed biochemical assays to study the role of TERT in the calcification process using primary tissues and valve interstitial cells (VICs) from control and CAVD patients, smooth muscle cells (SMCs) from WT and Tert knockout mice, and mesenchymal stem cells (MSCs). Results: We found that TERT protein is highly expressed in calcified aortic valves and VICs isolated from patients with calcified valves, compared to healthy valves. VICs can be induced to calcify under osteogenic differentiation conditions, and we found that TERT accumulated after fourteen days in this culture, with no effect on either telomere length, proliferation, or senescence. We expanded the scope of our approach by evaluating TERT's influence on calcification of mice aortic smooth muscle cells (mSMCs). We found WT mSMCs readily calcified in vitro, but mSMCs from Tert knockout mice did not, and Tert deletion also reduced valve calcification in a Ldlr / Tert double knockout mice model compared to Ldlr knockout alone. In VICs, shRNA mediated TERT downregulation reduced expression of RUNX2 . Finally, we found that inflammatory signals intensify in vitro calcification, induce TERT expression, and we show evidence that TERT interacts with STAT5. Conclusion: Our data suggest that TERT is required for valve calcification by stimulating transcriptional pathways promoting the osteogenic transition of quiescent VICs into calcifying VICs in the aortic valve. These results indicate that TERT is an active contributor to the calcification process of valve tissues.


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