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Subsequent Decrease (subsequent + decrease)
Selected AbstractsMineral Paragenesis of the Lepanto Copper and Gold and the Victoria Gold Deposits, Mankayan Mineral District, PhilippinesRESOURCE GEOLOGY, Issue 2 2001Rene Juna R. CLAVERIA Abstract: Mineral paragenesis of the alteration, ore and gangue minerals of the Lepanto epithermal copper-gold deposit and the Victoria gold deposit, Mankayan Mineral District, Northern Luzon, Philippines, is discussed. The principal ore minerals of the Lepanto copper-gold deposit are enargite and luzonite, with significant presence of tennantite-tetrahedrite, chalcopyrite, sphalerite, galena, native gold/electrum and gold-silver tellurides. Pervasive alteration zonations are commonly observed from silicification outward to advanced argillic then to propylitic zone. The ore mineralogy of the Lepanto copper-gold deposit suggests high fS2 in the early stages of mineralization corresponding to the deposition of the enargite-luzonite-pyrite assemblage. Subsequent decrease in the fS2 formed the chalcopyrite-tennantite-pyrite assemblage. An increase in the fS2 of the fluids with the formation of the covellite-digenite-telluride assemblage caused the deposition of native gold/electrum and gold-silver tellurides. The principal ore minerals of the Victoria gold deposit are sphalerite, galena, chalcopyrite, tetrahedrite and native gold/electrum. The alteration halos are relatively narrow and in an outward sequence from the ore, silica alteration grades to illitic-argillic alteration, which in turn grades to propylitic alteration. The Victoria gold mineralization has undergone early stages of silica supersaturation leading to quartz deposition. Vigorous boiling increased the pH of the fluids that led to the deposition of sulfides and carbonates. The consequent decrease in H2S precipitated the gold. Gypsum and anhydrite mainly occur as overprints that cut the carbonate-silica stages. The crosscutting and overprinting relationships of the Victoria quartz-gold-base metal veins on the Lepanto copper-gold veins manifest the late introduction of near neutral pH hydrothermal fluids. [source] Ammonium perchlorate effects on thyroid function and growth in bobwhite quail chicksENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2004F. M. ANNE Mcnabb Abstract Bobwhite quail chicks were used to investigate ammonium perchlorate (AP; NH4ClO4) effects on thyroid function and growth. Beginning at 3 to 4 d posthatch, we evaluated organismal thyroid status (circulating hormones), activation of the hypo-thalamic-pituitary-thyroid axis (thyroid wt) and thyroidal hormone content over a wide range of AP concentrations (50 ,g/L , 4,000 mg/L) in drinking water, for relatively short (2-week) and longer (8-week) exposures. Thyroidal thyroxine (T4) content, the most sensitive index of decreased thyroid function, decreased markedly in response to increasing perchlorate exposure. Thyroid weight and plasma T4 were less sensitive indicators and similar in their ability to detect thyroid changes. Growth measurements (body wt and skeletal growth) were very insensitive indices. Because thyroids contain large hormone stores, with low exposures or short time periods, these stores can be used to maintain circulating hormones, at least temporarily. Most depletion of thyroidal T4 occurred during the first two weeks of AP exposure. Subsequent decreases were at a slower rate presumably because thyrotropin stimulation of the thyroids at least partially compensated for some of the perchlorate effect. Additional studies of the interactions between AP concentration and exposure time are needed for understanding the complex nature of thyroid responses to perchlorate. [source] (,)Epigallocatechingallate protects the mitochondria against the deleterious effects of lipids, calcium and adenosine triphosphate in isoproterenol induced myocardial infarcted male Wistar ratsJOURNAL OF APPLIED TOXICOLOGY, Issue 8 2008P. T. Devika Abstract The present study was undertaken to evaluate the protective effect of (,)epigallocatechin gallate (EGCG) on mitochondrial lipids, lipid peroxides, Na+/K+ ATPase, calcium and adenosine triphosphate in isoproterenol (ISO) induced myocardial infarction in male Wistar rats. Rats were pretreated with EGCG (30 mg kg,1 body weight) orally using an intragastric tube daily for a period of 21 days. After that, ISO (100 mg kg,1 body weight) was subcutaneously injected to rats at intervals of 24 h for two days. ISO induced rats showed significant increase in the levels of cholesterol, triglycerides and free fatty acids with subsequent decrease in the levels of phospholipids in mitochondrial fraction of the heart. ISO induction also caused significant increase in lipid peroxidation products (thiobarbituric acid reactive substances and lipid hydroperoxides) and significant decrease in the activity of Na+/K+ ATPase in mitochondrial fraction of the heart. A significant increase in the levels of calcium and significant decrease in the levels of adenosine triphosphate were observed in ISO-induced mitochondrial heart. Prior treatment with EGCG (30 mg kg,1) significantly protected these alterations and maintained normal mitochondrial function. Thus, this study confirmed the protective effect of EGCG on mitochondria in experimentally induced cardiotoxicity in Wistar rats. Copyright © 2008 John Wiley & Sons, Ltd. [source] Overexpression of human copper/zinc-superoxide dismutase in transgenic animals attenuates the reduction of apurinic/apyrimidinic endonuclease expression in neurons after in vitro ischemia and after transient global cerebral ischemiaJOURNAL OF NEUROCHEMISTRY, Issue 2 2005Purnima Narasimhan Abstract Oxidative stress after ischemia/reperfusion has been shown to induce DNA damage and subsequent DNA repair activity. Apurinic/apyrimidinic endonuclease (APE) is a multifunctional protein in the DNA base excision repair pathway which repairs apurinic/apyrimidinic sites in DNA. We investigated the involvement of oxidative stress and expression of APE in neurons after oxygen,glucose deprivation and after global cerebral ischemia. Our results suggest that overexpression of human copper/zinc-superoxide dismutase reduced oxidative stress with a subsequent decrease in APE expression. Production of oxygen free radicals and inhibition of the base excision repair pathway may play pivotal roles in the cell death pathway after ischemia. [source] Coral Cover Change Associated to El Niño, Eastern Pacific, Costa Rica, 1992,2001MARINE ECOLOGY, Issue 3 2003Carlos E. Jiménez Abstract., Changes in live and dead coral cover were documented at three localities off the Costa Rican central Pacific coast first in 1992 during the aftermath of the 1991,1992 El Niño; again in the period between 1994 and 1995, and last in January 2001. Recovery of coral communities after the 1991,1992 El Niño was expressed by a significant increase (,40 %) in 1994 of live coral cover at one locality (Manuel Antonio). A subsequent decrease (,50 %) in response to the very strong 1997,1998 episode was recorded at Manuel Antonio and Ballena, mainly due to partial tissue mortality of branching (Pocillopora spp.) and massive (Porites lobata) corals. Mortality of entire colonies associated to that event was scarce and confined to branching and nodular (Psammocora stellata) corals. This species was not found at one locality (Cambutal) in the 2001 survey and it is presumed locally extinct. The recovery of this coral and others will depend on recruits from surviving colonies in deeper waters and other coral communities in the vicinity. Within sites at a given locality, contrasting results in live coral cover variability were found. This is partially due to distinct coral assemblages, coral growth, physical exposure to tidal regime, and, related to the latter, variable duration and intensity of the warming event. In general, predominant meteorological conditions at the studied area are conducive to solar radiation (UV) stress during El Niño years and are related to changes in the atmosphere-ocean interactions in response to the warming events. [source] The G1 cell cycle arrest of macrophages infected with Aggregatibacter actinomycetemcomitansORAL DISEASES, Issue 3 2010H Kasai Oral Diseases (2010) 16, 305,309 Objectives:, Infection of murine macrophage cell line J774.1 with the periodontopathic bacterium Aggregatibacter actinomycetemcomitans induces apoptotic cell death. The infection induces cell cycle arrest in the G1 phase prior to the appearance of apoptotic cells. This study determined the involvement of various cell cycle-related signal molecules in A. actinomycetemcomitans-induced G1 cell cycle arrest. Materials and Methods:, Cell cycle in J774.1 cells infected with A. actinomycetemcomitans was analyzed with a flow cytometer. Immunoblot analysis was also employed to determine the expression levels of intracellular signal molecules. Results:, Flow cytometric analysis revealed that the percentage of cells in the G1 phase increased to 77.2% at 12 h after A. actinomycetemcomitans infection. Additionally, according to immunoblot analysis, expression levels of hyperphosphorylated forms of retinoblastoma protein (ppRb) declined in J774.1 cells following A. actinomycetemcomitans infection, whereas hypophosphorylated Rb (pRb) expression levels were elevated slightly. Expression levels of cyclin D1 and D2 in the cells decreased gradually postinfection; CDK2, CDK4, CDK6 and cyclin E levels were not changed. Furthermore, postinfection, p21CIP1/WAF1 expression increased at 6 h, followed by a subsequent decrease. Conclusion:, These findings suggest that cyclin D1 and D2 and p21CIP1/WAF1 participate in G1 cell cycle arrest in A. actinomycetemcomitans-infected J774.1 cells. [source] Integration of proximate and evolutionary explanation of reproductive strategy: The case of callitrichid primates and implications for human biologyAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 6 2009Suzette D. Tardif We offer examples of how proximate and evolutionary forms of argument may inform each other in better understanding reproductive strategy in callitrichid primates, the smallest of the anthropoid primates. In addition, we illustrate how comparative approaches, when applied judiciously, can aid in the formulation of hypotheses regarding even seemingly unique traits within a taxonomic group. In the first example, examination of the nature of genetics in cytokine systems that leads to altered ovulation number in sheep suggests some relatively simple changes could explain both the adaptation of increased ovulation number in marmosets and the subsequent decrease in ovulation number in the closely related species, callimico. In the second example, the role of body size and phylogeny in explaining the role of maternal energy constraints upon gestation and lactation is explored, leading to additional hypotheses regarding these relations in a species that is both small but also in a phylogenetic line selected for slow reproduction. Finally, the role of comparative data in the study of proximate and evolutionary explanations of "unique" human reproductive strategies is discussed. Am. J. Hum. Biol., 2009. © 2009 Wiley-Liss, Inc. [source] Sequence dependence of ,-hairpin structure: Comparison of a salt bridge and an aromatic interactionPROTEIN SCIENCE, Issue 12 2003Sarah E. Kiehna Abstract A comparison of the contributions and position dependence of cross-strand electrostatic and aromatic side-chain interactions to ,-sheet stability has been performed by using nuclear magnetic resonance in a well-folded ,-hairpin peptide of the general sequence XRTVXVdPGOXITQX. Phe,Phe and Glu,Lys pairs were varied at the internal and terminal non,hydrogen-bonded position, and the resulting stability was measured by the effects on ,-hydrogen and aromatic hydrogen chemical shifts. It was determined that the introduction of a Phe,Phe pair resulted in a more folded peptide, regardless of position, and a more tightly folded core. Substitution of the Glu,Lys pair at the internal position results in a less folded peptide and increased fraying at the terminal residues. Upfield shifting of the aromatic hydrogens provided evidence for an edge-face aromatic interaction, regardless of position of the Phe,Phe pair. In peptides with two Phe,Phe pairs, substitution with Glu,Lys at either position resulted in a weakening of the aromatic interaction and a subsequent decrease in peptide stability. Thermal denaturation of the peptides containing Phe,Phe indicates that the aromatic interaction is enthalpically favored, whereas the folding of hairpins with cross-strand Glu,Lys pairs was less enthalpically favorable but entropically more favorable. [source] Are long subglacial bedforms indicative of fast ice flow?BOREAS, Issue 3 2002CHRIS R. STOKES It has been suggested that extremely long subglacial bedforms (e.g. attenuated drumlins and mega-scale glacial lineations) record former areas of fast-flowing ice and that bedform elongation ratio is a useful proxy for ice velocity. Despite the availability of much data pertaining to the measurement and analysis of subglacial bed-forms, these assumptions have rarely been explicitly addressed in detail. In this paper, we demonstrate that long subglacial bedforms (length:width ratios 10:1) are indicative of fast ice flow. Using satellite imagery, we mapped over 8000 lineaments associated with a highly convergent flow pattern near Dubawnt Lake, District of Keewatin, Canada. This flow pattern is unusual in that it displays a large zone of convergence feeding into a main ,trunk' and then diverging towards the inferred ice margin. The ,bottleneck' pattern is taken to record an increase and subsequent decrease in ice velocity and we analysed transverse and longitudinal variations in bedform morphometry. The main trunk of the flow pattern (down-ice of the convergent zone) is characterized by mega-scale glacial lineations of great length (up to 13 km) and high elongation ratios (up to 43:1). The down-ice variations in elongation ratio reflect exactly what we would expect from a terrestrial ice stream whose velocity increases in the onset zone passes through a maximum in the main trunk and slows down as the ice diverges at the terminus. It is suggested that any unifying theory of drumlin formation must be able to account for the association between long subglacial bedforms and fast ice flow, although it is not assumed that fast ice flow always produces attenuated bedforms. A further implication of this work is that many more ice streams may be identified on the basis of attenuated subglacial bedforms, radically altering our views on the flow dynamics of former ice sheets. [source] Expression of aquaporins in the efferent ductules, sperm counts, and sperm motility in estrogen receptor-, deficient mice fed lab chow versus caseinMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 2 2006Ricardo Ruz Abstract Estrogens play an important role in the male reproductive tract, and this is especially so for the efferent ductules, where ,-estrogen receptors (ER,) have been localized. Mice deficient in ER, (,ERKO mice) are infertile, and the effect appears to be due in part to retention of water at the level of the efferent ductules. In the present study, we examined the consequences of ER, deletion on the distribution of certain aquaporins (AQPs), water protein channels, in the efferent ductules and on sperm numbers and motility. In addition, the effects of feeding mice a regular lab chow diet, which contains phytoestrogens, known to affect male reproductive tract functions, and a casein diet, which lacks phytoestrogens, were also assessed. Light microscope immunolocalizations of AQP-1 and AQP-9 revealed dramatic reduction and patchier staining in ,ERKO mice with distal areas of the efferent ductules being more affected than proximal areas. No other changes in immunolocalizations were noted as a consequence of diet. Computer-assisted sperm analyses demonstrated a 62% reduction in cauda epididymal sperm/ml in ,ERKO mice fed lab chow, whereas 87% fewer sperm/ml were observed in ,ERKO mice fed casein, suggesting an enhanced role for sperm production and concentration in a diet containing phytoestrogens. All sperm motility parameters were altered to some degree in ,ERKO mice fed lab chow. Alterations in sperm motility parameters were also detected, but were less dramatic in ,ERKO mice fed casein. These data suggest that the decrease in AQP expression in the efferent ductules of ,ERKO mice contributes in part to water retention in this tissue, eventually leading to backflow of water into the testis, with subsequent decreases in sperm concentration and motility. The data also suggest that phytoestrogens, which are present in regular lab chow, can influence the male reproductive tract with and without the presence of ER,, promoting efferent ductule and epididymal functions when ER, is expressed, but inhibiting these same functions when ER, is missing. Taken together the data underscore the importance of estrogens and ER, in maintaining sperm maturation and preventing male infertility. Mol. Reprod. Dev. © 2005 Wiley-Liss, Inc. [source] Utilization of nanoscale zero-valent iron for source remediation,A case studyREMEDIATION, Issue 2 2006Keith W. Henn A pilot-scale study was performed using a palladium-catalyzed and polymer-coated nanoscale zero-valent iron (ZVI) particle suspension at the Naval Air Station in Jacksonville, Florida. A total of 300 pounds of nanoscale ZVI particle suspension was injected via a gravity feed and recirculated through a source area containing chlorinated volatile organic compounds (VOCs). The recirculation created favorable mixing and distribution of the iron suspension and enhanced the mass transfer of sorbed and nonaqueous constituents into the aqueous phase, where the contaminants could be reduced. Between 65 and 99 percent aqueous-phase VOC concentration reduction occurred, due to abiotic degradation, within five weeks of the injection. The rapid abiotic degradation processes then yielded to slower biological degradation as subsequent decreases in -elimination parameters were observed,yet favorable redox conditions were maintained as a result of the ZVI treatment. Post-treatment analyses revealed cumulative reduction of soil contaminant concentrations between 8 and 92 percent. Aqueous-phase VOC concentrations in wells side gradient and downgradient of the source were reduced up to 99 percent and were near or below applicable regulatory criteria. These reductions, coupled with the generation of innocuous by-products, indicate that nanoscale ZVI effectively degraded contamination and reduced the mass flux from the source, a critical metric identified for source treatment. A summary of this project was recently presented at the US EPA Workshop on Nanotechnology for Site Remediation in Washington, D.C., on October 21,22, 2005. This case study supplied evidence that nanoscale zero valent iron, an emerging remediation technology, has been implemented successfully in the field. More information about this workshop and this presentation can be found at www.frtr.gov/nano/index.htm. © 2006 Wiley Periodicals, Inc. [source] | ||||||||||||||||