Textural and geochemical features of freshwater microbialites from Laguna Bacalar, Quintana Roo, Mexico

Microbialites provide some of the oldest direct evidence of life on Earth. They reached their peak during the Proterozoic and declined afterward. Their decline has been attributed to grazing and/or burrowing by metazoans, to changes in ocean chemistry, or to competition with other calcifying organisms. The freshwater microbialites at Laguna Bacalar (Mexico) provide an opportunity to better understand microbialite growth in terms of interaction between grazing organisms versus calcium carbonate precipitation. The Laguna Bacalar microbialites are described in terms of their distinct mesostructures. Stromatolites display internal lamination, attributed to the precipitation of calcite and the upward migration of cyanobacteria during periods of low sedimentation. Thrombolitic stromatolites show internal lamination in addition to internal clotting. The clotting is seen as a result of binding and/or trapping of micritic peloids by cyanobacteria and attributed to periods of high sedimentation. The carbonates in both microbialites had similar C- and O-stable–isotopic signatures, both enriched in ^(13)C relative to bivalves, suggesting photosynthetic CO_2 uptake was the trigger for carbonate precipitation. This implies that the rate of microbialite growth is largely a function of ambient carbonate saturation state, while the texture is especially dependent on accretion rates and sediment deposition on their surface. Importantly, the coexistence with grazing animals suggests no significant inhibition on microbialite growth, thereby calling into question the decline of microbialite as a result of metazoan evolution. Varying sedimentation rates are likely important in controlling the distribution of thrombolite–stromatolite packages in the geological record, given the importance of this factor at Bacalar

The Isolation and Characterization of β-Glucogallin as a Novel Aldose Reductase Inhibitor from Emblica officinalis

Diabetes mellitus is recognized as a leading cause of new cases of blindness. The prevalence of diabetic eye disease is expected to continue to increase worldwide as a result of the dramatic increase in the number of people with diabetes. At present, there is no medical treatment to delay or prevent the onset and progression of cataract or retinopathy, the most common causes of vision loss in diabetics. The plant Emblica officinalis (gooseberry) has been used for thousands of years as a traditional Indian Ayurvedic preparation for the treatment of diabetes in humans. Extracts from this plant have been shown to be efficacious against the progression of cataract in a diabetic rat model. Aldose reductase (ALR2) is implicated in the development of secondary complications of diabetes including cataract and, therefore, has been a major drug target for the development of therapies to treat diabetic disease. Herein, we present the bioassay-guided isolation and structure elucidation of 1-O-galloyl-β-D-glucose (β-glucogallin), a major component from the fruit of the gooseberry that displays selective as well as relatively potent inhibition (IC50 = 17 µM) of AKR1B1 in vitro. Molecular modeling demonstrates that this inhibitor is able to favorably bind in the active site. Further, we show that β-glucogallin effectively inhibits sorbitol accumulation by 73% at 30 µM under hyperglycemic conditions in an ex-vivo organ culture model of lenses excised from transgenic mice overexpressing human ALR2 in the lens. This study supports the continued development of natural products such as β-glucogallin as therapeutic leads in the development of novel therapies to treat diabetic complications such as cataract

METhodological RadiomICs Score (METRICS): a quality scoring tool for radiomics research endorsed by EuSoMII

Purpose: To propose a new quality scoring tool, METhodological RadiomICs Score (METRICS), to assess and improve research quality of radiomics studies. Methods: We conducted an online modified Delphi study with a group of international experts. It was performed in three consecutive stages: Stage#1, item preparation; Stage#2, panel discussion among EuSoMII Auditing Group members to identify the items to be voted; and Stage#3, four rounds of the modified Delphi exercise by panelists to determine the items eligible for the METRICS and their weights. The consensus threshold was 75%. Based on the median ranks derived from expert panel opinion and their rank-sum based conversion to importance scores, the category and item weights were calculated. Result: In total, 59 panelists from 19 countries participated in selection and ranking of the items and categories. Final METRICS tool included 30 items within 9 categories. According to their weights, the categories were in descending order of importance: study design, imaging data, image processing and feature extraction, metrics and comparison, testing, feature processing, preparation for modeling, segmentation, and open science. A web application and a repository were developed to streamline the calculation of the METRICS score and to collect feedback from the radiomics community. Conclusion: In this work, we developed a scoring tool for assessing the methodological quality of the radiomics research, with a large international panel and a modified Delphi protocol. With its conditional format to cover methodological variations, it provides a well-constructed framework for the key methodological concepts to assess the quality of radiomic research papers. Critical relevance statement: A quality assessment tool, METhodological RadiomICs Score (METRICS), is made available by a large group of international domain experts, with transparent methodology, aiming at evaluating and improving research quality in radiomics and machine learning. Key points: • A methodological scoring tool, METRICS, was developed for assessing the quality of radiomics research, with a large international expert panel and a modified Delphi protocol. • The proposed scoring tool presents expert opinion-based importance weights of categories and items with a transparent methodology for the first time. • METRICS accounts for varying use cases, from handcrafted radiomics to entirely deep learning-based pipelines. • A web application has been developed to help with the calculation of the METRICS score (https://metricsscore.github.io/metrics/METRICS.html) and a repository created to collect feedback from the radiomics community (https://github.com/metricsscore/metrics). Graphical Abstract: [Figure not available: see fulltext.

Integración geológica de la Península de Paria, estado Sucre, Venezuela

El cinturón móvil marginal al N de Suramérica en la región de la península de Paria es una zona en la cual pueden ser reconocidos bloques litosfericos que en su conjunto muestran patrones complejos y variables de deformación convergente, que corno consecuencia de desplazamientos oblicuos post-Eocenos diron lugar a ía imbricación tectónica del margen pasivo Mesozoico de Suramérica, lo que ocurrió de manera diacrónica de oeste a este. El proceso deriva finalmente en la sutura parcial de un arco insular remanente, resultante de un proceso de subducción que se desarrolló al ONO de Paria entre el Cretácico y el Paleogéno. Dicho arco es parte integrante de la placa Caribe que, en su traslación relativa hacia el este, ha generado una zona limitrofe predominantemente transpresiva que se extiende a los largo del límite norte de Suramérica. En el área de estudio y zonas aledañas, gran parte de esta deformación es acumulada en el desplazamiento de hasta 120 km del Sistema de Fallas de El Pilar, el cual limita dos provincias con historias geológicas distintas, a! sur la serranía del Interior Oriental y al norte el cinturón ígneo-metamórfico conformado por la parte oriental de cordillera de La Costa. La falla de El Pilar acumula un desplazamiento dextral asociado a un particionamiento de esfuerzos post-Eoceno; hacia el Mioceno tardío reacomodos del margen generan una migración de la zona principal de desplazamiento desde el Sistema El Pilar hacia el Sistema Los Bajos, dando lugar al desarrollo de una cuenca tensional oblicua en el golfo de Paria. ES cinturon ígneo-metamórfico de Paria es definido como un orógeno de doble vergencia generado como consecuencia de ía convergencia oblicua entre las placas Caribe y Suramérica (CRUZ 2005); dos terrenos pueden ser reconocidos en este orógeno: el primero, de carácter para-autóctono, está conformado por los depósitos profundos de la cuenca de margen pasivo, acretados conjuntamente con fragmentos del basamento granítico (SPEED etal. 1997). Se yuxtapone a este terreno parte de la corteza oceánica mesozoica, y quizás depósitos de antearco cretácicos, definiendo una provincia alóctona, cuyo límite se produce a lo largo de la zona de falla de Coche - North Coast, un sistema transtensionaí que ocurre en la costa norte. Ambos terrenos se encuentran afectados por un metamorfismo en la facies de! esquisto verde, no obstante su historia metamórfica es distinta. El terreno alóctono fue afectado por un metamorfismo retrogradadante generado en la zona de subducción mesozoica, donde se alcanzaron condiciones que permitieron neogénesis mineral en las facies del esquisto azul y del esquisto verde, posteriormente todos estos minerales serian reequilibrados bajo la facies del esquisto verde. El último evento de metamorfismo alcanza la zona de la clorita y localmente la de la biotita; es probable que las condiciones de metamorfismo que afectan las secuencias de margen pasivo sean consecuencia del emplazamiento del terreno alóctono durante el Mioceno medio, :-:*rx> lo revelan análisis mAr/ 39Ar efectuados por speed et al. (1997) en micas metamórficas del Gneis de El ftfaogo En el margen activo del Mioceno de Venezuela nororiental cuencas antepaís periféricas reciben depósitos fíysch, e! levantamiento asociado a la convergencia oblicua genera la migración lateral de estas cuencas, donde e! transporte de masas se produce por difusión latera! en ambientes marinos limitados ai norte por el cinturón ígneo- metemórfíco, sur por el combamiento (forebuldge) oblicuo asociado a arreglos litosféricos derivados del avance del frente de létormación desde el NNO y al este por una zona de subducción convergencia al oeste, asociada a dicha zona ocurre in magmatismo con una afinidad de arco de islas, expuesta al sur de Campano la unidad Riolita Porfídica de Carúpano es una evidencia remanente del extinto arco. Diacrónicamente se desarrollaban ambientes deltaicos, que coo el inicio de la sutura en el sector occidental pasan a ser recubiertos por depósitos molásicos, son estos ambientes continentales y transicionales los que caracterizan Ja sedimentación del pleistoceno al sur de Paria, ocurriendo desde El Pilar hasta Güiria. A continuación se presenta una tabla resumen de las unidades tectono-estratigráfícas que r-eden ser reconocidas en la península de Paria, se incluyen las siglas empleadas en los 33 mapas a escala 1:25.000 ¿enerados fundamentalmente con datos de superficie obtenidos por tesistas UCV 1964-1969, para el desarrollo de los mismos, se utilizaron técnicas de cartografía digital coadyuvantes para ía mejora de la cartografía geológica, éstas incluyen modelos de elevación e iluminación y sombra: El uso de dichas técnicas hizo posible definir dos provincias morfo-estructurales separadas por el valle diagonal de río Grande, generado por fallas que definen una zona transtensíonal que disecta el orógeno. l. NIDADES SEDIMENTARIAS Qha Qhh Qhar Qmm Qht Medios depüsitaeionales recientes Holoceno - Cuaternario Valle Qcal Valíe coluvio- aluvial Qal Valle aluvial Planicie litoral marina Qhcf Cordón o flecha Albuferas Planicie cenagosa herbácea Planicie cenagosa arbolada Manglar marino fiínacionaí (slikke) Cubeta de marea (turbera) Planicie de desbordamiento Qet Explayamiento terminal Pieistoceno Superior - Holoceno Valle Qpal Valle aluvial Pleistoceno Superior Planicie litoral marina Qpd Dunas Piedemanie Qpe3 Explayamíento Qpe2 Explayamiento Qpcd Cono de deyección Qpr2 Rampa de expíayamtento Pleistoceno Inferior Piedemonie Qpae Abanico de explayamiento Planicie de desbordamiento Qpet Explayamiento terminal Bajos de ablación Qprd Rampa de denudación Planicie de explayamiento Qppp Planicie piedemontina Depósitos en cuencas sucesoras acrecionales y post-ac racionales Terciario Qpg Formación Güiria Qrs Formación Río Salado Qpm Formación Mesa Tmar Formación Los Arroyos Depósitos de margen pasivo Cretácico Temprano Kb Formación Barranquin Kc Formación El Cantil Ksa Formación San Antonio UNIDADES ÍGNEO- METAMORFICAS Intrusivas asociadas al ATT de las Antillas Menores Tercia rio (Mioceno Tardío) Te Riolita porfídica de Campano Alóctonas con afinidas MORB y/o AIT Cretácico Temprano (Aptiense) Kec Metaígneas de El Copey Kec3g Metagabro Kec3p Metaperidotita Kecl s Serpentinita Kec3a Melange tectónico Metasedimentarias de margen pasivo Cretácico Temprano (Barremiense - Aptiense (?)) Kc Esquisto de Campano Kcq Esquisto de Cariaquito Kcqp Mármol de Patao Kcqy Esquisto de Yacua Ku Esquisto de Uquire Kg Metasedimentarias de Gíiinimita Jurásico Tardío - Cretácico Temprano JKt Esquisto de Tunaput JKma Esquisto de Macuro JKmah Mármol de Yaguaraparo JKmah Marmol de La Horqueta JKmag Esquisto de Guatay Fragmentos de basamento granítico Paleozoico Carbonífero Pzcd Gneis de El Dragón Pzcm Gneis de El Mang

The trace metal content of modern and ancient shallow marine dolomites: significance and systematics

Dolomitization has traditionally been regarded as being related to the interaction of thermally active Mg-rich fluids with poorly ordered carbonate precursors of elusive origin. Our ideas on how such precursors form have evolved rapidly since the late 1990s, and microbes are now considered key players — i.e., by providing nucleation sites and due to their capacity to regulate pore water alkalinity. Outstanding questions include what triggers the low-temperature reactions conducive to dolomite stabilization and whether or not subsurface chemolithotrophs participate in the catalysis of these reactions. Here these aspects are evaluated throughout three independent but complementary textural and spectroscopic examinations of shallow marine dolomites. First, fine-scale analyses of modern carbonate cements point to biologically mediated manganese and sulfur co-recycling as a necessary control for dolomite stabilization. Second, similar analyses of mid-Cretaceous dolomitic marlstones suggest that in the Aptian-Albian epicontinental sea of northern South America, dolomite precipitation was linked to the utilization of metals and sulfur for organic matter respiration. Reactants were transported to the extended shallow marine setting in association with episodic orbital perturbations, which also triggered high organic matter productivity and burial, and ultimately led to interstitial organogenic dolomite formation. Third, stromatolitic rocks from the Paleoproterozoic Gunflint Formation (Ontario, Canada) were interrogated in order to interpret the variable redox states of pore waters at the time of stromatolite accretion and diagenetic mineral stabilization. This study shows that diagenetic shifts associated with exogenous water mixing, together with variable burial and exhumation histories, led to the development of the temporarily and spatially restricted reaction fronts responsible for the pervasive replacement of early formed carbonate cements. Such diagenetic complexity adds difficulty to the interpretation of paleomarine geochemical conditions. Overall, this work reveals that the trace metal content of shallow marine dolomite provides information useful for the evaluation of redox conditions that govern mineral authigenesis. However, autocycles and their effect on the activity of subsurface microbes, and thus over the saturation state of minerals in coastal sediments should be carefully considered prior to regional scale paleoceanographic interpretations