In its Sixth Edition, this book has been updated and revised to incorporate new information on technology, economic, and political issues that have impacted the use of fluids to drill and complete ...oil and gas wells. With updated content on completion fluids and reservoir drilling fluids; health, safety and environment; drilling fluid systems and products; new fluid systems and additives from both chemical and engineering perspectives; wellbore stability, adding the new R&D on water-based muds; and equipment and procedures for evaluating drilling fluid performance in light of the advent of digital technology and better manufacturing techniques, this book has been thoroughly updated to meet the drilling and completion engineer's needs.
The many major developments that have taken place in the field of oil well drilling fluids technology have called for a total rewriting of the late Walter F. Rogers' classic reference source. This ...Fourth Edition describes the latest innovations and refinements of drilling fluids technology and remains the essential guide to a complex area of petroleum production.
estimate of the number of tropical tree species Slik, J. W. Ferry; ViÌctor Arroyo-RodriÌiÌguez; Patricia Alvarez-Loayza ...
Proceedings of the National Academy of Sciences - PNAS,
06/2015, Letnik:
112, Številka:
24
Journal Article, Web Resource
Recenzirano
Odprti dostop
Significance People are fascinated by the amazing diversity of tropical forests and will be surprised to learn that robust estimates of the number of tropical tree species are lacking. We show that ...there are at least 40,000, but possibly more than 53,000, tree species in the tropics, in contrast to only 124 across temperate Europe. Almost all tropical tree species are restricted to their respective continents, and the Indo-Pacific region appears to be as species-rich as tropical America, with each of these two regions being almost five times as rich in tree species as African tropical forests. Our study shows that most tree species are extremely rare, meaning that they may be under serious risk of extinction at current deforestation rates.
The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisherâs alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between â¼40,000 and â¼53,000, i.e., at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of â¼19,000â25,000 tree species. Continental Africa is relatively depauperate with a minimum of â¼4,500â6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa.
REPLY TO BAILEY ET AL Paredes, F.; Lassègue, B.; Williams, H. C. ...
Proceedings of the National Academy of Sciences,
08/2018, Letnik:
115, Številka:
32
Journal Article
Recenzirano
Odprti dostop
This article is a reply to Bailey et al.: New perspectives on the novel role of the Poldip2/ACSM1 axis in a functional mammalian lipoylation salvage pathway. While sharing sequence homology with the ...bacterial lipoate-protein ligase A (lplA), LIPT1 is distinct in that it catalyzes only the last of the two-step reaction that involves activation of lipoate (yielding lipoyl-AMP as an intermediate), followed by transfer to the apoenzyme. Thus, in contrast to lplA, LIPT1-dependent protein lipoylation occurs only when provided with lipoyl-AMP, indicating that it uses activated lipoate as a substrate. The recent crystallization of LIPT1 with tightly bound lipoyl-AMP confirms this notion. Well-established literature, including the identification of mammalian Ac-CoA synthetase medium-chain family member 1 (ACSM1) as a mitochondrial enzyme with unique lipoate-activating activity, suggests that the combined effects of ACSM1/LIPT1 reconstitute lplA activity, as demonstrated in vitro.
Phylogenetic classification of the world’s tropical forests Franklin, Janet; Arroyo-Rodríguez, Víctor; Aguirre, Nikolay ...
Proceedings of the National Academy of Sciences - PNAS,
02/2018, Letnik:
115, Številka:
8
Journal Article, Web Resource
Recenzirano
Odprti dostop
Knowledge about the biogeographic affinities of the world’s tropical forests helps to better understand regional differences in forest structure, diversity, composition, and dynamics. Such ...understanding will enable anticipation of region-specific responses to global environmental change. Modern phylogenies, in combination with broad coverage of species inventory data, now allow for global biogeographic analyses that take species evolutionary distance into account. Here we present a classification of the world’s tropical forests based on their phylogenetic similarity. We identify five principal floristic regions and their floristic relationships: (i) Indo-Pacific, (ii) Subtropical, (iii) African, (iv) American, and (v) Dry forests. Our results do not support the traditional neo- versus paleotropical forest division but instead separate the combined American and African forests from their Indo-Pacific counterparts. We also find indications for the existence of a global dry forest region, with representatives in America, Africa, Madagascar, and India. Additionally, a northern-hemisphere Subtropical forest region was identified with representatives in Asia and America, providing support for a link between Asian and American northern-hemisphere forests.
Local vasodilation in response to hypoxia is a fundamental physiologic response ensuring oxygen delivery to tissues under metabolic stress. Recent studies identify a role for the red blood cell ...(RBC), with hemoglobin the hypoxic sensor. Herein, we investigate the mechanisms regulating this process and explore the relative roles of adenosine triphosphate, S-nitrosohemoglobin, and nitrite as effectors. We provide evidence that hypoxic RBCs mediate vasodilation by reducing nitrite to nitric oxide (NO) and ATP release. NO dependence for nitrite-mediated vasodilation was evidenced by NO gas formation, stimulation of cGMP production, and inhibition of mitochondrial respiration in a process sensitive to the NO scavenger C-PTIO. The nitrite reductase activity of hemoglobin is modulated by heme deoxygenation and heme redox potential, with maximal activity observed at 50% hemoglobin oxygenation (P50). Concomitantly, vasodilation is initiated at the P50, suggesting that oxygen sensing by hemoglobin is mechanistically linked to nitrite reduction and stimulation of vasodilation. Mutation of the conserved β93cys residue decreases the heme redox potential (ie, decreases E1/2), an effect that increases nitrite reductase activity and vasodilation at any given hemoglobin saturation. These data support a function for RBC hemoglobin as an allosterically and redox-regulated nitrite reductase whose “enzyme activity” couples hypoxia to increased NO-dependent blood flow.
The reliance of many cancers on aerobic glycolysis has stimulated efforts to develop lactate dehydrogenase (LDH) inhibitors. However, despite significant efforts, LDH inhibitors (LDHi) with ...sufficient specificity and in vivo activity to determine whether LDH is a feasible drug target are lacking. We describe an LDHi with potent, on-target, in vivo activity. Using hyperpolarized magnetic resonance spectroscopic imaging (HP-MRSI), we demonstrate in vivo LDH inhibition in two glycolytic cancer models, MIA PaCa-2 and HT29, and we correlate depth and duration of LDH inhibition with direct anti-tumor activity. HP-MRSI also reveals a metabolic rewiring that occurs in vivo within 30 min of LDH inhibition, wherein pyruvate in a tumor is redirected toward mitochondrial metabolism. Using HP-MRSI, we show that inhibition of mitochondrial complex 1 rapidly redirects tumor pyruvate toward lactate. Inhibition of both mitochondrial complex 1 and LDH suppresses metabolic plasticity, causing metabolic quiescence in vitro and tumor growth inhibition in vivo.
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•Specific LDH inhibition in vivo reduces growth rate of glycolytic tumors•Depth and duration of tumor LDH inhibition can be monitored in real time by HP-MRSI•LDH inhibition in vivo redirects pyruvate to support oxidative phosphorylation•Inhibiting mitochondrial complex 1 and LDH enhances durability of anti-tumor response
Oshima et al. use hyperpolarized magnetic resonance spectroscopy to dynamically monitor tumor glycolysis and oxidative phosphorylation. LDH inhibition slows tumor growth but rapidly redirects pyruvate to support mitochondrial metabolism. Inhibiting both mitochondrial complex 1 and LDH suppresses metabolic plasticity of glycolytic tumors in vivo, significantly prolonging tumor growth inhibition.
Altered cellular metabolism, including an increased dependence on aerobic glycolysis, is a hallmark of cancer. Despite the fact that this observation was first made nearly a century ago, effective ...therapeutic targeting of glycolysis in cancer has remained elusive. One potentially promising approach involves targeting the glycolytic enzyme lactate dehydrogenase (LDH), which is overexpressed and plays a critical role in several cancers. Here, we used a novel class of LDH inhibitors to demonstrate, for the first time, that Ewing sarcoma cells are exquisitely sensitive to inhibition of LDH. EWS-FLI1, the oncogenic driver of Ewing sarcoma, regulated LDH A (LDHA) expression. Genetic depletion of LDHA inhibited proliferation of Ewing sarcoma cells and induced apoptosis, phenocopying pharmacologic inhibition of LDH. LDH inhibitors affected Ewing sarcoma cell viability both
and
by reducing glycolysis. Intravenous administration of LDH inhibitors resulted in the greatest intratumoral drug accumulation, inducing tumor cell death and reducing tumor growth. The major dose-limiting toxicity observed was hemolysis, indicating that a narrow therapeutic window exists for these compounds. Taken together, these data suggest that targeting glycolysis through inhibition of LDH should be further investigated as a potential therapeutic approach for cancers such as Ewing sarcoma that exhibit oncogene-dependent expression of LDH and increased glycolysis. SIGNIFICANCE: LDHA is a pharmacologically tractable EWS-FLI1 transcriptional target that regulates the glycolytic dependence of Ewing sarcoma.
Mitochondria morphology and function, and their quality control by mitophagy, are essential for heart function. We investigated whether these are influenced by time of the day (TOD), sex, and fed or ...fasting status, using transmission electron microscopy (EM), mitochondrial electron transport chain (ETC) activity, and mito-QC reporter mice. We observed peak mitochondrial number at ZT8 in the fed state, which was dependent on the intrinsic cardiac circadian clock, as hearts from cardiomyocyte-specific BMAL1 knockout (CBK) mice exhibit different TOD responses. In contrast to mitochondrial number, mitochondrial ETC activities do not fluctuate across TOD, but decrease immediately and significantly in response to fasting. Concurrent with the loss of ETC activities, ETC proteins were decreased with fasting, simultaneous with significant increases of mitophagy, mitochondrial antioxidant protein SOD2, and the fission protein DRP1. Fasting-induced mitophagy was lost in CBK mice, indicating a direct role of BMAL1 in regulating mitophagy. This is the first of its kind report to demonstrate the interactions between sex, fasting, and TOD on cardiac mitochondrial structure, function and mitophagy. These studies provide a foundation for future investigations of mitochondrial functional perturbation in aging and heart diseases.
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