Crustal shortening and thickening to c. 70-85 km in the Tibetan Plateau occurred both before and mainly after the c. 50 Ma India-Asia collision. Potassic-ultrapotassic shoshonitic and adakitic lavas ...erupted across the Qiangtang (c. 50-29 Ma) and Lhasa blocks (c. 30-10 Ma) indicate a hot mantle, thick crust and eclogitic root during that period. The progressive northward underthrusting of cold, Indian mantle lithosphere since collision shut off the source in the Lhasa block at c. 10 Ma. Late Miocene-Pleistocene shoshonitic volcanic rocks in northern Tibet require hot mantle. We review the major tectonic processes proposed for Tibet including "rigid-block', continuum and crustal flow as well as the geological history of the major strike-slip faults. We examine controversies concerning the cumulative geological offsets and the discrepancies between geological, Quaternary and geodetic slip rates. Low present-day slip rates measured from global positioning system and InSAR along the Karakoram and Altyn Tagh Faults in addition to slow long-term geological rates can only account for limited eastward extrusion of Tibet since Mid-Miocene time. We conclude that despite being prominent geomorphological features sometimes with wide mylonite zones, the faults cut earlier formed metamorphic and igneous rocks and show limited offsets. Concentrated strain at the surface is dissipated deeper into wide ductile shear zones.
Catechins are widely occurring in our diet and beverages. The cancer-preventive activities of catechins have been extensively studied. Of these, (-)-epigallocatechin-3-gallate (EGCG), the principal ...catechin in green tea, has received the most attention. The inhibitory activities of tea catechins against carcinogenesis and cancer cell growth have been demonstrated in a large number of laboratory studies. Many mechanisms for modulating cancer signaling and metabolic pathways have been proposed based on numerous studies in cell lines with EGCG, the most active tea catechin. Nevertheless, it is not known whether many of these mechanisms indeed contribute to the anti-cancer activities in animals and in humans. Human studies have provided some results for the cancer preventive activities of tea catechins; however, the activities are not strong. This article reviews the cancer preventive activities and mechanisms of action of tea catechins involving their redox activities, biochemical properties and binding to key enzymes or signal transduction proteins. These mechanisms lead to suppression of cell proliferation, increased apoptosis and inhibition of angiogenesis. The relevance of the proposed mechanisms for cancer prevention are assessed in the light of the situation in vivo. The potential and possible problems in the application of tea and tea-derived products for cancer prevention are discussed.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
This article presents a brief overview of studies on the prevention of cancer and cardiometabolic diseases by tea. The major focus is on green tea catechins concerning the effective doses used, the ...mechanisms of action, and possible toxic effects. In cancer prevention by tea, the laboratory results are strong; however, the human data are inconclusive, and the effective doses used in some human trials approached toxic levels. In studies of the alleviation of metabolic syndrome, diabetes, and prevention of cardiovascular diseases, the results from human studies are stronger in individuals who consume 3–4 cups of tea (600–900 mg of catechins) or more per day. The tolerable upper intake level of tea catechins has been set at 300 mg of (−)-epigallocatechin-3-gallate in a bolus dose per day in some European countries. The effects of doses and dosage forms on catechin toxicity, the mechanisms involved, and factors that may affect toxicity are discussed.
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IJS, KILJ, NUK, PNG, UL, UM, UPUK
Southeast Asia consists of several microcontinents that detached from the northeastern margin of Gondwanaland. The Song Ma belt in northern Vietnam consists of ophiolite, metabasite, metasedimentary ...rocks and eclogite, and it is thought to be a suture zone between the Indochina and South China blocks. However, the nature and boundaries of the Song Ma belt and the collision age of the two blocks have long been debated. In this article, petrological and geochemical studies on the Song Ma ophiolite and eclogite and first sensitive high‐resolution ion microprobe (SHRIMP) age dating of eclogite provide new light to resolve such debate. Eclogite consisting of garnet, omphacite, phengite, quartz, barroisite and rutile is closely associated with garnet–phengite–quartz schist in the ‘Nam Co antiform’, a northern subunit of the Song Ma belt. The eclogite experienced a three‐stage metamorphic evolution: (I) pre‐eclogite stage (amphibolite facies) defined by inclusions of taramite, barroisite, quartz, zoisite/epidote, mica, rutile & rare chlorite in garnet, (II) eclogite stage and (III) retrograde stage of amphibolite to greenschist facies. The P–T conditions of the three stages are of 14–16 kbar and 520–550 °C (I), 24–27 kbar and 650–750 °C (II), and 3–7 kbar and 430–510 °C (III), and show a clockwise P–T path based on their mineral assemblages and stability fields in the P–T pseudosection. Thermobarometric results yield similar peak pressure and temperature (26–28 kbar and 650–710 °C). These data suggest that the Song Ma eclogite underwent high‐pressure metamorphism in subduction zone with a low thermal gradient ∼8 °C km−1. The Song Ma ophiolite is composed of serpentinized peridotite, gabbro, basalt, mafic dyke and chert, and experienced ocean‐floor metamorphism. Metabasalt and gabbro of ophiolite suite and eclogite all have MORB‐type geochemical affinities. Zircon separates from eclogite have very low Th/U ratios of 0.01–0.05, indicating a metamorphic origin. SHRIMP U–Pb isotopic analyses of this zircon yield a 206Pb/238U weighted mean age of 230.5 ± 8.2 Ma. This age is interpreted as the closure age of the Paleotethys Ocean that separated the South China and Indochina blocks, and the subsequent collision of the two blocks that took place at the Middle Triassic corresponding to the major episode of the Indosinian Orogeny.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Tea, made from the leaves of the plant Camellia sinensis, is a popular beverage and the possible beneficial health effects of tea polyphenols (TPP) have been studied extensively. This article ...discusses the biological fates of TPP and their interactions with the microbiota in the gastrointestinal tract. TPP are absorbed mainly in the small intestine and undergo metabolism in different organs. The unabsorbed TPP entering the colon are degraded by microbiota. Some of the metabolites are also absorbed systemically and excreted in the urine, while those unabsorbed are excreted in the feces. TPP can in turn modify the composition of gut microbiota. In the human and rodent studies reviewed herein, many studies reported a correlation between the observed microbiota changes with lowering blood glucose level or body weight gain. Bacteria species belonging to different genera were identified; however, the effects of TPP at the phyla level were inconsistent among studies. Our recent study identified a few co-abundance groups that were correlated with the blood glucose lowering effect of green tea polyphenols. The "guilds" approach that we used could lead to a more systematic analysis of microbiota changes. The mechanisms by which TPP modulate gut microbiota directly, or through influence on nutrient environment, are discussed. Finally, there are discussions on how the interactions of TPP with microbiota may impact metabolic diseases as well as on some future studies that are needed.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Three principal granite provinces are defined across SE Asia, as follows. (1) The Western Thailand-Myanmar/Burma province consists of hornblende-biotite I-type granodiorite-granites and felsic ...biotite-K-feldspar (± garnet ± tourmaline) granites associated with abundant tin mineralization in greisen-type veins. New ion microprobe U-Pb dating results from Phuket Island show zircon core ages of 212 ± 2 and 214 ± 2 Ma and a thermal overprint with rims of 81.2 ± 1.2 and 85-75 Ma. (2) The North Thailand-West Malaya Main Range province has mainly S-type biotite granites and abundant tin mineralization resulting from crustal thickening following collision of the Sibumasu plate with Indochina during the Mid-Triassic. Biotite granites around Kuala Lumpur contain extremely U-rich zircons (up to 38000 ppm) that yield ages of 215 ± 7 and 210 ± 7 Ma. (3) The East Malaya province consists of dominantly Permian-Triassic I-type hornblende-biotite granites but with subordinate S-type plutons and A-type syenite-gabbros. Biotite-K-feldspar granites from Tioman Island off the east coast of Malaysia also yield a zircon age of 80 ± 1 Ma, showing Cretaceous magmatism in common with province 1. Geological and U-Pb geochronological data suggest that two east-dipping (in present-day coordinates) subduction zones are required during the Triassic, one along the Bentong-Raub Palaeo-Tethyan suture, and the other west of the Phuket-Burma province 1 belt. SUPPLEMENTARY MATERIAL: A full description of U-Pb analytical methods used and data tables are available at www.geolsoc.org.uk/SUP18523.
The formation of the vascular network is an intricate and complex process that is an obligate requirement during vertebrate development. The cardiovascular system is the first organ to develop and ...reach a functional state, which underscores the crucial role of the vasculature in the developing embryo. The development of the vasculature into highly branched conduits needs to occur in numerous sites and in precise patterns to supply oxygen and nutrients to the rapidly expanding tissue of the embryo. This process is mediated by the coordinated response of vascular endothelial and mural cells to the heterogeneous angiogenic cues provided by tissues and organs, whereas aberrant regulation and coordination of angiogenic signals during development result in lethality, impaired organ development, or disease states. This article reviews the essential signaling pathways required for establishment of the vertebrate vasculature with a major focus on a key regulatory factor, vascular endothelial growth factor (VEGF). We also discuss current knowledge of physiological angiogenic processes as well as their disruptions in pathological processes, particularly tumorigenesis.
Tea, made from leaves of the plant Camellia sinensis, Theaceae, has been used by humans for thousands of years, first as a medicinal herb and then as a beverage that is consumed widely. For the past ...25 years, tea has been studied extensively for its beneficial health effects, including prevention of cancer, reduction of body weight, alleviation of metabolic syndrome, prevention of cardiovascular diseases, and protection against neurodegenerative diseases. Whether these effects can be produced by tea at the levels commonly consumed by humans is an open question. This review examines these topics and elucidates the common mechanisms for these beneficial health effects. It also discusses other health effects and possible side effects of tea consumption. This article provides a critical assessment of the health effects of tea consumption and suggests new directions for research in this area.
Tea, a popular beverage made from leaves of the plant Camellia sinensis, has been shown to reduce body weight, alleviate metabolic syndrome, and prevent diabetes and cardiovascular diseases in animal ...models and humans. Such beneficial effects have generally been observed in most human studies when the level of tea consumption was three to four cups (600–900 mg tea catechins) or more per day. Green tea is more effective than black tea. In spite of numerous studies, the fundamental mechanisms for these actions still remain unclear. From a review of the literature, we propose that the two major mechanisms are: (i) decreasing absorption of lipids and proteins by tea constituents in the intestine, thus reducing calorie intake; and (ii) activating AMP‐activated protein kinase by tea polyphenols that are bioavailable in the liver, skeletal muscle, and adipose tissues. The relative importance of these two mechanisms depends on the types of tea and diet consumed by individuals. The activated AMP‐activated protein kinase would decrease gluconeogenesis and fatty acid synthesis and increase catabolism, leading to body weight reduction and metabolic syndrome alleviation. Other mechanisms and the health relevance of these beneficial effects of tea consumption remain to be further investigated.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The world is in the midst of the COVID-19 pandemic. In this comprehensive review, we discuss the potential protective effects of (−)-epigallocatechin-3-gallate (EGCG), a major constituent of green ...tea, against COVID-19.
Information from literature of clinical symptoms and molecular pathology of COVID-19 as well as relevant publications in which EGCG shows potential protective activities against COVID-19 is integrated and evaluated.
EGCG, via activating Nrf2, can suppress ACE2 (a cellular receptor for SARS-CoV-2) and TMPRSS2, which mediate cell entry of the virus. Through inhibition of SARS-CoV-2 main protease, EGCG may inhibit viral reproduction. EGCG via its broad antioxidant activity may protect against SARS-CoV-2 evoked mitochondrial ROS (which promote SARS-CoV-2 replication) and against ROS burst inflicted by neutrophil extracellular traps. By suppressing ER-resident GRP78 activity and expression, EGCG can potentially inhibit SARS-CoV-2 life cycle. EGCG also shows protective effects against 1) cytokine storm-associated acute lung injury/acute respiratory distress syndrome, 2) thrombosis via suppressing tissue factors and activating platelets, 3) sepsis by inactivating redox-sensitive HMGB1, and 4) lung fibrosis through augmenting Nrf2 and suppressing NF-κB. These activities remain to be further substantiated in animals and humans. The possible concerted actions of EGCG suggest the importance of further studies on the prevention and treatment of COVID-19 in humans. These results also call for epidemiological studies on potential preventive effects of green tea drinking on COVID-19.
•EGCG may impede SARS-CoV-2 infection by activating Nrf2 which downregulates ACE2 and TMPRSS2.•EGCG may suppress SARS-CoV-2 replication via inhibiting SARS-CoV-2 main protease, mitochondrial ROS and ER-resident GRP78.•EGCG may protect against ROS burst inflicted by SARS-CoV-2 induced neutrophil extracellular traps.•EGCG may decrease SARS-CoV-2 triggered cytokine storm, sepsis, thrombosis and lung fibrosis.•EGCG may prevent diabetes comorbidity risk in COVID-19 patients.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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