Showing papers by "University of Costa Rica published in 2003"
TL;DR: The anammox reaction is shown to be a globally significant sink for oceanic nitrogen in the anoxic waters of Golfo Dulce, a 200-m-deep coastal bay in Costa Rica, where it accounts for 19–35% of the total N2 formation in the water column.
Abstract: In oxygen-depleted zones of the open ocean, and in anoxic basins and fjords, denitrification (the bacterial reduction of nitrate to give N2) is recognized as the only significant process converting fixed nitrogen to gaseous N2. Primary production in the oceans is often limited by the availability of fixed nitrogen such as ammonium or nitrate1, and nitrogen-removal processes consequently affect both ecosystem function and global biogeochemical cycles. It was recently discovered that the anaerobic oxidation of ammonium with nitrite—the ‘anammox’ reaction, performed by bacteria—was responsible for a significant fraction of N2 production in some marine sediments2. Here we show that this reaction is also important in the anoxic waters of Golfo Dulce, a 200-m-deep coastal bay in Costa Rica, where it accounts for 19–35% of the total N2 formation in the water column. The water-column chemistry in Golfo Dulce is very similar to that in oxygen-depleted zones of the oceans—in which one-half to one-third of the global nitrogen removal is believed to occur3,4. We therefore expect the anammox reaction to be a globally significant sink for oceanic nitrogen.
623 citations
Trinity College, Dublin1, National Institutes of Health2, University of Pennsylvania3, University College London4, Indiana University – Purdue University Indianapolis5, University of Birmingham6, Johns Hopkins University School of Medicine7, Icahn School of Medicine at Mount Sinai8, University of Chicago9, University of Helsinki10, University of Antwerp11, University of California, San Diego12, Garvan Institute of Medical Research13, University of New South Wales14, Laval University15, University of Utah16, University of Edinburgh17, Washington University in St. Louis18, University of California, Los Angeles19, University of Bonn20, Dalhousie University21, University of Ottawa22, McGill University23, Université libre de Bruxelles24, Umeå University25, University of California, Irvine26, Macquarie University27, University of Texas Health Science Center at San Antonio28, University of California, San Francisco29, University of Costa Rica30, Aarhus University Hospital31, Odense University Hospital32, University of Geneva33, Hacettepe University34
TL;DR: The present results for the very narrow model are promising but suggest that more and larger data sets are needed to support linkage, as well as suggest that linkage might be detected in certain populations or subsets of pedigrees.
Abstract: Genome scans of bipolar disorder (BPD) have not produced consistent evidence for linkage. The rank-based genome scan meta-analysis (GSMA) method was applied to 18 BPD genome scan data sets in an effort to identify regions with significant support for linkage in the combined data. The two primary analyses considered available linkage data for "very narrow" (i.e., BP-I and schizoaffective disorder-BP) and "narrow" (i.e., adding BP-II disorder) disease models, with the ranks weighted for sample size. A "broad" model (i.e., adding recurrent major depression) and unweighted analyses were also performed. No region achieved genomewide statistical significance by several simulation-based criteria. The most significant P values (<.01) were observed on chromosomes 9p22.3-21.1 (very narrow), 10q11.21-22.1 (very narrow), and 14q24.1-32.12 (narrow). Nominally significant P values were observed in adjacent bins on chromosomes 9p and 18p-q, across all three disease models on chromosomes 14q and 18p-q, and across two models on chromosome 8q. Relatively few BPD pedigrees have been studied under narrow disease models relative to the schizophrenia GSMA data set, which produced more significant results. There was no overlap of the highest-ranked regions for the two disorders. The present results for the very narrow model are promising but suggest that more and larger data sets are needed. Alternatively, linkage might be detected in certain populations or subsets of pedigrees. The narrow and broad data sets had considerable power, according to simulation studies, but did not produce more highly significant evidence for linkage. We note that meta-analysis can sometimes provide support for linkage but cannot disprove linkage in any candidate region.
585 citations
TL;DR: Although both leaf and xylem characters are correlated with the response of stomata to Y L, there is considerable flexibility in this linkage and the range of responses is discussed in terms of the differing leaf-loss strategies exhibited by these species.
Abstract: This study examined the linkage between xylem vulnerability, stomatal response to leaf water potential ( Y L ), and loss of leaf turgor in eight species of seasonally dry tropical forest trees. In order to maximize the potential variation in these traits species that exhibit a range of leaf habits and phenologies were selected. It was found that in all species stomatal conductance was responsive to Y L over a narrow range of water potentials, and that Y L inducing 50% stomatal closure was correlated with both the Y L inducing a 20% loss of xylem hydraulic conductivity and leaf water potential at turgor loss in all species. In contrast, there was no correlation between the water potential causing a 50% loss of conductivity in the stem xylem, and the water potential at stomatal closure ( Y Y Y SC ) amongst species. It was concluded that although both leaf and xylem characters are correlated with the response of stomata to Y L, there is considerable flexibility in this linkage. The range of responses is discussed in terms of the differing leaf-loss strategies exhibited by these species.
410 citations
TL;DR: A model is presented to explain the difference between PLA2s that induce predominantly local myonecrosis and those inducing both local and systemic myotoxicity, and the former bind not only to muscle cells, but also to other cell types, thereby precluding a systemic distribution of thesePLA2s.
384 citations
TL;DR: It is proposed that all the toxic activities of Lys49 PLA2s are related to their ability to destabilize natural and artificial membranes, using a cationic/hydrophobic effector site located at their C-terminal loop.
299 citations
TL;DR: Genetic analysis revealed that the progeny of trees from con- tinuous populations experienced lower levels of relatedness, a tendency for higher levels of outcrossing, and/ or more sires than isolated trees.
Abstract: The results of several studies suggest that forest fragmentation affects the mating patterns and re- productive success of tropical tree species by reducing pollinator activity, pollen deposition, and outcrossing levels. The flowering synchrony of trees has also been proposed as an additional factor in controlling fruit set and regulating levels of outcrossing, particularly in disturbed habitats. We examined the effects of forest frag- mentation and flowering phenology on the reproductive success and genetic structure of the progeny pro- duced by the tropical tree Pachira quinata . We conducted our study in the dry forest of Costa Rica and com- pared trees in two density and environmental conditions: (1) isolated trees separated by 500 m from other adult conspecifics and located in disturbed sites and (2) trees from continuous populations of groups of 20 or more reproductive individuals per hectare surrounded by undisturbed mature forest. Our study was con- ducted in the Guanacaste Conservation Area, Costa Rica, and surrounding areas. To evaluate flowering phe- nology, trees were classified as having synchronous or asynchronous flowering. The phenological stage of in- dividuals was classified according to the proximity of the peak flowering date of each tree with respect to the mean peak flowering of the rest of the population. Six percent of the flowers produced a fruit in trees from continuous populations, whereas in isolated trees only 3% of the flowers did so. Fruit set was not affected by the flowering phenology of trees but was influenced mainly by factors associated with forest fragmentation. Seed production per fruit was not affected by forest fragmentation or flowering phenology. Overall, total fruit production per tree was not affected by forest fragmentation, because isolated trees tended to produce more flowers than trees from continuous populations. Genetic analysis revealed that the progeny of trees from con- tinuous populations experienced lower levels of relatedness, a tendency for higher levels of outcrossing, and/ or more sires than isolated trees. Our results suggest that forest fragmentation can have an effect on the mat- ing patterns of P. quinata , reducing the number of outcross sires represented in the progeny of isolated trees.
248 citations
Book•
01 Jan 2003TL;DR: This book discusses the Workerless Social Parasites of the New World Pheidole, Based on the Queen, and the Species Groups of the Nonparasitic New World pheidole based on the Worker Castes.
Abstract: * Introduction * The Origins of Hyperdiversity * Glossary and Anatomy * Keys * The Workerless Social Parasites of the New World Pheidole, Based on the Queen * The Species Groups of the Nonparasitic New World Pheidole, Based on the Worker Castes * The aberrans Group * The biconstricta Group * The crassicornis Group * The diligens Group * The distorta Group * The fallax Group * The flavens Group * The gertrudae Group * The granulata Group * The lamia Group * The megacephala Group * The perpusilla Group * The pilifera Group * The punctatissima Group * The scrobifera Group * The tachigaliae Group * The teneriffana Group * The transversostriata Group * The tristis Group * The New World Species * Indeterminate Names * References * Acknowledgments * Index
238 citations
TL;DR: It is concluded that neutrophils do not play a significant role in the acute local pathological alterations induced by the venom of B. asper, and neutrophil play a prominentrole in the process of skeletal Muscle Nerve 28: 449–459, 2003.
Abstract: Local tissue damage induced by crotaline snake venoms includes edema, myonecrosis, hemorrhage, and an inflammatory response associated with a prominent cellular infiltrate. The role of neutrophils in the local tissue damage induced by Bothrops asper snake venom and by myotoxin I, a phospholipase A2 isolated from this venom, was investigated. Male Swiss mice were pretreated with either an antimouse granulocyte rat monoclonal immunoglobulin G (IgG) antibody or with isotype-matched control antibody. No significant differences in these local effects were observed between mice pretreated with antigranulocyte antibodies and those receiving control IgG. Moreover, myotoxicity induced by B. asper myotoxin I was similar in neutrophil-depleted and control mice. The role of neutrophils in the process of skeletal muscle regeneration was also assessed. Muscle regeneration was assessed by quantifying the muscle levels of creatine kinase and by morphometric histological analysis of the area comprised by regenerating cells in damaged regions of skeletal muscle. Mice depleted of neutrophils and then injected with B. asper venom showed a more deficient regenerative response than mice pretreated with control IgG. Moreover, a drastic difference in the regenerative response was observed in mice injected with myotoxin I, because animals pretreated with control IgG showed a successful regeneration, whereas those depleted of neutrophils had abundant areas of necrotic tissue that had not been removed 7 days after injection, associated with reduced contents of creatine kinase. It is concluded that (1) neutrophils do not play a significant role in the acute local pathological alterations induced by the venom of B. asper, and (2) neutrophils play a prominent role in the process of skeletal muscle regeneration after injection of B. asper venom and myotoxin I, probably related to the phagocytosis of necrotic material and the recruitment of other inflammatory cells, two events directly associated with a successful muscle regenerative response.
192 citations
TL;DR: The genetic similarity of the populations from Antioquia and the CVCR together with differences in LD between them should be exploitable for the identification and fine mapping of shared disease-related gene variants.
Abstract: We report a comparative genetic characterization of two population isolates with parallel demographic histories: the Central Valley of Costa Rica (CVCR) and Antioquia (in northwest Colombia). The analysis of mtDNA, Y-chromosome and autosomal polymorphisms shows that Antioquia and the CVCR are genetically very similar, indicating that closely related parental populations founded these two isolates. In both populations, the male ancestry is predominantly European, whereas the female ancestry is mostly Amerind. In agreement with their isolation, the Amerindian mtDNA diversity of Antioquia and the CVCR is typical of ethnically-defined native populations and is markedly lower than in other Latin American populations. A comparison of linkage disequilibrium (LD) at 18 marker pairs in Antioquia and the CVCR shows that markers in LD in both populations are located at short genetic distances (<~1 cM), whereas markers separated by greater distances are in LD only in the CVCR. This difference probably reflects stochastic variation of LD at the limited number of genome regions compared. The genetic similarity of the populations from Antioquia and the CVCR together with differences in LD between them should be exploitable for the identification and fine mapping of shared disease-related gene variants.
178 citations
TL;DR: Heterogeneity in pharmacokinetics and mechanism of action of venom components requires a detailed analysis of each venom-antivenom system in order to determine the most appropriate type of neutralising molecule for each particular venom.
Abstract: Parenteral administration of horse- and sheep-derived antivenoms constitutes the cornerstone in the therapy of envenomations induced by animal bites and stings. Depending on the type of neutralising molecule, antivenoms are made of: (i) whole IgG molecules (150 kDa), (ii) F(ab′)2 immunoglobulin fragments (100 kDa) or (iii) Fab immunoglobulin fragments (50 kDa). Because of their variable molecular mass, these three types of antivenoms have different pharmacokinetic profiles. Fab fragments have the largest volume of distribution and readily reach extravascular compartments. They are catabolised mainly by the kidney, having a more rapid clearance than F(ab′)2 fragments and IgG. On the other hand, IgG molecules have a lower volume of distribution and a longer elimination half-life, showing the highest cycling through the interstitial spaces in the body. IgG elimination occurs mainly by extrarenai mechanisms. F(ab′)2 fragments display a pharmacokinetic profile intermediate between those of Fab fragments and IgG molecules. Such diverse pharmacokinetic properties have implications for the pharmacodynamics of these immunobiologicals, since a pronounced mismatch has been described between the pharmacokinetics of venoms and antivenoms. Some venoms, such as those of scorpions and elapid snakes, are rich in low-molecular-mass neurotoxins of high diffusibility and large volume of distribution that reach their tissue targets rapidly after injection. In contrast, venoms rich in high-molecular-mass toxins, such as those of viperid snakes, have a pharmacokinetic profile characterised by a rapid initial absorption followed by a slow absorption process from the site of venom injection. Such delayed absorption has been linked with recurrence of envenomation when antibody levels in blood decrease. This heterogeneity in pharmacokinetics and mechanism of action of venom components requires a detailed analysis of each venom-antivenom system in order to determine the most appropriate type of neutralising molecule for each particular venom. Besides having a high affinity for toxicologically relevant venom components, an ideal antivenom should possess a volume of distribution as similar as possible to that of the toxins being neutralised. Moreover, high levels of neutralising antibodies should remain in blood for a relatively prolonged time to assure neutralisation of toxins reaching the bloodstream later in the course of envenomation, and to promote redistribution of toxins from extravascular compartments to blood. Additional studies are required on different venoms and antivenoms in order to further understand the pharmacokinetic-pharmacodynamic relationships of antibodies and their fragments and to optimise the immunotherapy of envenomations.
173 citations
TL;DR: It is shown that a member of the CDT family causes DNA double‐strand breaks in naturally intoxicated cells, acting as a true genotoxic agent, and the existence of a novel signalling pathway for intracellularly triggered activation of the RhoA GTPase via the ATM kinase in response to DNA damage is disclosed.
Abstract: Articulo cientifico -- Universidad de Costa Rica. Instituto de Investigaciones en Salud, 2003. Este documento es privado debido a limitaciones de derechos de autor.
TL;DR: It is suggested that phenological patterns of the Bombacaceae family in Neotropical dry forests are mainly constrained by phylogenetic membership and adaptive selective pressures associated with competition for pollinators.
Abstract: We compared phenological patterns of tree species of the family Bombacaceae in three seasonal forests in Mexico and Costa Rica whose dry seasons vary in duration and intensity. The objectives were to (1) determine intraspecific variation in phenology between sites in different geographic locations with different precipitation regimes, (2) compare interspecific phenological patterns within sites during one year, and (3) document seasonal pollinator use of floral resources at one site in relation to the flowering phenology of these species. To determine the sequence of phenological events in trees of the family Bombacaceae across three study sites, phenology of marked individuals was recorded every 2 wk from September 2000 through August 2001 for six species. To estimate the importance of bombacaceous species in the diet of nectarivorous bats, pollen samples were collected from the bodies or feces of bats once every 2 wk during flowering. Our study suggests that phenological patterns of the Bombacaceae family in Neotropical dry forests are mainly constrained by phylogenetic membership and adaptive selective pressures associated with competition for pollinators. Abiotic factors related to precipitation and soil water content appear to be regulating leaf flushing and abscission, but the principal causes of flowering are related to ultimate factors associated with competition for pollinators. This study is the first that evaluates the phenological pattern of species and genera of the same family at different latitudes in a similar life zone. Phenological events in plants may be affected by various factors that can be classified as proximate or ultimate causes. Proximate causes principally include short-term environmental events that may trigger phenological patterns, while ultimate causes include evolutionary forces that are responsible for these patterns. Environmental cues such as changes in water level stored by plants (Reich and Borchert, 1984; Borchert, 1994; but see Wright and Cornejo, 1990; Wright, 1991), seasonal variations in rainfall (Opler et al., 1976), changes in temperature (Ashton et al., 1988; Williams-Linera, 1997), photoperiod (Leopold, 1951; Tallak Nilsen and Huller, 1981; van Schaik, 1986; Rivera et al., 2002), irradiance (Wright and van Schaik, 1994), and sporadic climatic events (Sakai et al., 1999) have been mentioned as proximate causes triggering phenological events in tropical plants. In forests with a marked dry season, changes in water availability from shifts in precipitation regimes and soil moisture have been proposed as the es
TL;DR: Routinely trichromatic species ingested leaves that were “red shifted—compared to background foliage more frequently than species lacking this trait, suggesting a preference for optimal nutritive gain.
Abstract: Evolution of the red-green visual subsystem in trichromatic primates has been linked to foraging advantages, namely the detection of either ripe fruits or young leaves amid mature foliage. We tested competing hypotheses globally for eight primate taxa: five with routine trichromatic vision, three without. Routinely trichromatic species ingested leaves that were "red shifted" compared to background foliage more frequently than species lacking this trait. Observed choices were not the reddest possible, suggesting a preference for optimal nutritive gain. There were no similar differences for fruits although red-greenness may sometimes be important in close-range fruit selection. These results suggest that routine trichromacy evolved in a context in which leaf consumption was critical.
TL;DR: Sequence and structural comparisons of hemorrhagic and nonhemorrhagic P‐I metalloproteinases from snake venoms revealed differences in several regions, which may influence the interaction of these enzymes with physiologically relevant substrates in the extracellular matrix.
Abstract: BaP1 is a 22.7-kD P-I-type zinc-dependent metalloproteinase isolated from the venom of the snake Bothrops asper, a medically relevant species in Central America. This enzyme exerts multiple tissue-damaging activities, including hemorrhage, myonecrosis, dermonecrosis, blistering, and edema. BaP1 is a single chain of 202 amino acids that shows highest sequence identity with metalloproteinases isolated from the venoms of snakes of the subfamily Crotalinae. It has six Cys residues involved in three disulfide bridges (Cys 117–Cys 197, Cys 159–Cys 181, Cys 157–Cys 164). It has the consensus sequence H142E143XXH146XXGXXH152, as well as the sequence C164I165M166, which characterize the “metzincin” superfamily of metalloproteinases. The active-site cleft separates a major subdomain (residues 1–152), comprising four -helices and a five-stranded -sheet, from the minor subdomain, which is formed by a single -helix and several loops. The catalytic zinc ion is coordinated by the N2 nitrogen atoms of His 142, His 146, and His 152, in addition to a solvent water molecule, which in turn is bound to Glu 143. Several conserved residues contribute to the formation of the hydrophobic pocket, and Met 166 serves as a hydrophobic base for the active-site groups. Sequence and structural comparisons of hemorrhagic and nonhemorrhagic P-I metalloproteinases from snake venoms revealed differences in several regions. In particular, the loop comprising residues 153 to 176 has marked structural differences between metalloproteinases with very different hemorrhagic activities. Because this region lies in close proximity to the active-site microenvironment, it may influence the interaction of these enzymes with physiologically relevant substrates in the extracellular matrix.
TL;DR: High 18:2 trans-FA in adipose tissue are associated with increased risk of myocardial infarction, and consumers should be aware of the harmful effects of products containing partially hydrogenated oils.
Abstract: Trans-fatty acid intake is associated with coronary heart disease (CHD), but the atherogenic potential of individual trans-fatty acids (FA) from partially hydrogenated oils (18:1 and 18:2) or meat and dairy products (16:1 and 18:1) is unclear. Incident cases (n = 482) of a first nonfatal myocardial infarction (MI) were matched with population controls (n = 482) for age, gender and area of residence, all living in Costa Rica. Trans-FA in adipose tissue samples were assessed by gas chromatography. Odds ratios (OR) and 95% confidence intervals were calculated from conditional logistic regression models. Total adipose tissue trans-fat was positively associated with risk of MI. After adjusting for established risk factors and other confounders, the OR by quintiles of total trans-fat were 1.00, 1.34, 2.05, 2.22 and 2.94 (P-test for trend < 0.01). This association was attributed mainly to 18:2 trans-FA that were abundant in both adipose tissue and in partially hydrogenated soybean oil, margarines and baked products used by this population; OR = 1.00, 0.96, 2.09, 3.51 and 5.05 (P-test for trend < 0.001). Adipose tissue 16:1 trans-FA were also associated with MI; OR = 1.00, 1.57, 1.39, 1.34 and 2.58 (P-test for trend < 0.05). An association with 18:1 trans-FA was not detected. High 18:2 trans-FA in adipose tissue are associated with increased risk of MI. Because the use of hydrogenated oils is increasing worldwide, consumers should be aware of the harmful effects of products containing partially hydrogenated oils.
TL;DR: Venom of adult specimens showed a higher number of peaks with indirect hemolytic activity than venom of newborn specimens, and polyvalent antivenom produced in Costa Rica recognized all the bands of both venoms from specimens at all ages tested, when assayed by Western blotting.
TL;DR: The study demonstrates the negative effect that habitat disruption has on bat pollinators in tropical dry forest ecosystems and documents the negative consequences for the plants they pollinate.
Abstract: In the tropical dry forest of the central Pacific coast of Mexico the pollination and reproductive success of the bombacaceous tree Ceiba grandiflora was nega- tively affected by habitat disruption. Two of the three bat species that function as effective pollinators for this species (Glossophaga soricina and Musonycteris har- risoni) visited flowers found in trees in disturbed habitats significantly less than trees found in undisturbed habitats. A similar pattern was observed for the effective bat pollinator, Leptonycteris curasoae; however the differ- ence was not significant. The three nectarivorous bats that functioned as effective pollinators of C. grandiflora also visited flowers to exclusively feed on pollen by biting or pulling off an anther (see Fig. S1 of Electronic Supple- mentary Material). The number of pollen grains deposited on stigmas from flowers in undisturbed areas was significantly greater than from flowers in disturbed habitats. The greater visitation rate and the greater number of pollen grains deposited on flowers from trees in undisturbed forest resulted in a significantly greater fruit set for trees in these areas. Our study demonstrates the negative effect that habitat disruption has on bat pollinators in tropical dry forest ecosystems and docu- ments the negative consequences for the plants they pollinate. Electronic Supplementary Material Supplementary material is available for this article if you access the article at http://dx.doi.org/10.1007/s00442-003-1234-3. A link in the frame on the left on that page takes you directly to the supplementary material.
TL;DR: The implications of these new groups of PLA2 toxin inhibitors in the context of the current understanding of snake biology as well as in the development of novel therapeutic reagents in the treatment of snake envenomations worldwide are discussed.
TL;DR: In gas gangrene, Cp-PLC dysregulates transduction pathways in endothelial cells, platelets and neutrophils leading to the uncontrolled production of several intercellular mediators and adhesion molecules, enhancing the conditions for anaerobic growth.
TL;DR: The results suggest that Asp49 and Lys49 PLA(2)s are important hyperalgesic components of B. asper venom, and that Lys49 and Asp 49 PLA( 2)s exert their algogenic actions through different molecular mechanisms.
Journal Article•
TL;DR: The overall goal of Pan American CLIVAR Research on the North American Monsoon System is to determine the sources and limits of predictability of warm season precipitation over North America, with emphasis on time scales ranging up to seasonal-to-interannual as mentioned in this paper.
Abstract: The overall goal of Pan American CLIVAR Research on the North American Monsoon System is to determine the sources and limits of predictability of warm season precipitation over North America, with emphasis on time scales ranging up to seasonal-to-interannual. To achieve this goal, several research objectives have been identified including (1) a better understanding of the key components of the monsoon system and their temporal and spatial variability, (2) a better understanding of the role of this system within the global water cycle (3) improved observational data sets, and (4) improved simulation and monthly-to-seasonal prediction of the monsoon and regional water resources. The purpose of this paper is to review the recent progress made towards achieving these objectives and to highlight some of the future challenges based on gaps in our understanding.
TL;DR: Peptide AppK synthesized with D-amino acids retained both activities of the natural L-enantiomer, suggesting that its mechanism of action does not involve the recognition of a proteic receptor/acceptor site on muscle cells, but possibly the binding to other structures, such as negatively-charged membrane phospholipids.
TL;DR: Basparin A is likely to play an important role in the coagulopathy associated with B. asper envenoming, and activity is completely inhibited by Costa Rican polyvalent (Crotalinae) anti-venom.
01 Jan 2003
TL;DR: Coral communities, reefs, and isolated coral colonies can be found along the Pacific coast of Costa Rica and offshore islands as discussed by the authors, where the main impact on Pacific reefs has been bleaching and death of corals associated with El Nino warming events.
Abstract: Coral communities, reefs, and isolated coral colonies can be found along the Pacific coast of Costa Rica and offshore islands. In this chapter a brief history of research, and descriptions of the coral communities and reefs of the Pacific coast of Costa Rica are presented. On the north, the reefs are exposed to seasonal upwelling but they are well-developed and the growth rates of several species are higher than in non-upwelling areas. On the south, some reefs have been growing for over 5,000 years, resulting in thick accumulations. There are also reefs at Isla del Coco, 500 km from the coast. Species that are absent or rare in other eastern Pacific sites are found in Costa Rica, e.g. Porites rus and Leptoseris papyracea. The main impact on Pacific reefs has been bleaching and death of corals associated with El Nino warming events. Other reefs exposed to high sediment loads are greatly degraded. Most coral reefs and coral communities of the Pacific coast of Costa Rica are located within protected areas.
TL;DR: Calculations showed that nectar production in these flowers could drive a sink of sufficient magnitude to allow water input via the phloem equal to water lost from the flower to the atmosphere.
Abstract: Many trees in tropical dry forests flower during the dry season when evaporative demand is high and soil water levels are low. In this study the factors influencing the water balance of flowers from three species of dry forest trees were examined. Flowers had greater mucilage contents than leaves, high intrinsic and absolute capacitances, long time constants for water exchange and high transfer resistances. Flower water potentials were higher than in leaves and did not fluctuate over the lifespan of the flower. Flower water content also remained constant even though evaporation rates were high, suggesting that water was being supplied from the stem. In two of the species, the water potential gradient between flowers and leaves was opposite to that necessary for water transport from stem to flowers through the xylem, and it was therefore hypothesized that water may enter the flower through the phloem. Calculations showed that nectar production in these flowers could drive a sink of sufficient magnitude to allow water input via the phloem equal to water lost from the flower to the atmosphere.
TL;DR: In this article, the risk of acute myocardial infarction (MI) associated with consumption of individual saturated fatty acids (SFAs) and their food sources in Costa Rica was determined.
Abstract: Background: Epidemiological studies on the effect of individual saturated fatty acids (SFAs) on cardiovascular disease, especially in developing countries with different dietary patterns, are scarce. Objective: To determine the risk of nonfatal acute myocardial infarction (MI) associated with consumption of individual SFAs and their food sources in Costa Rica. Design: The cases (n=485) were survivors of a first acute MI and were matched by age, sex and area of residence to population controls (n=508). Data on anthropometrical measurements, lifestyle and diet were collected using interviewer-administered questionnaires. Results: In analyses adjusted for confounders, consumption of total and individual SFAs was associated with an increased risk of MI. The odds ratio (OR) (95% confidence intervals) for 1% increase in energy from total saturated fat was 1.12 (1.03–1.21) while it was 1.51 (1.03–2.22) for lauric acid+myristic acid, 1.14 (1.01–1.30) for palmitic acid and 2.00 (1.34–3.00) for stearic acid. Although lauric and myristic acids were associated with increased risk of MI, they were consumed in small amounts and most of the saturated fat (87%) came from palmitic and stearic acids, which derived mainly from red meat and fried foods. Consumption of cheese (1–2 vs 0 servings/day) was associated with increased risk of MI (OR=3.07; 95% confidence interval: 1.74–5.39; P for trend <0.0001), while consumption of low-fat milk was not. Conclusions: Increased consumption of total and individual SFAs is associated with increased risk of MI. Lauric, myristic and stearic acids were more potent than palmitic acid. Sponsorship: National Institutes of Health Grant HL 49086 and HL 60692.
TL;DR: The compound Cu3(dpa)4Cl2, 1 (dpa = the anion of dipyridylamine), which was first synthesized and characterized in 1990, has been structurally characterized in three new crystal forms having Cu...Cu separations of 2.47-2.49 A and the possible existence of an exchange pathway in which the metal atoms interact directly with each other.
Abstract: The compound Cu3(dpa)4Cl2, 1 (dpa = the anion of dipyridylamine), which was first synthesized and characterized in 1990, has been structurally characterized in three new crystal forms having Cu···Cu separations of 2.47−2.49 A. Its magnetic properties have been studied fully. Reaction of Cu3(dpa)4Cl2 with 2 equiv of silver tetrafluoroborate yields Cu3(dpa)4(BF4)2 (2), a compound with a similar linear trinuclear structure but coordinated BF4 anions in each axial position and having shorter Cu···Cu distances of 2.40 A but similar magnetic properties. Least squares fitting of the magnetic susceptibility data for 1 and 2 gave isotropic g values of 2.007 and 2.130 and exchange parameters of −373 and −411 cm-1, respectively. This suggests the possible existence of an exchange pathway in which the metal atoms interact directly with each other.
TL;DR: In this article, the role of the glaciers in the generation of seismicity for Cotopaxi volcano was quantified by comparing the seismic activity registered on the glacier and on the rock near the snout of the north flank glacier.
Abstract: [1] Significant seismic activity is generally recorded on volcanoes covered by an icecap. This work was carried out in order to quantify the role of the glaciers in the generation of seismicity for Cotopaxi volcano. We compared the seismic activity registered on the glacier and on the rock near the snout of the north flank glacier. We focused on the analysis of low frequency events (<5 Hz) similar to volcanic LP events when recorded on rock base. The particle motion analysis helps to estimate source locations, which are distributed in crevasses areas. High incident angles suggest a superficial origin. These events are interpreted as icequakes for which we propose as source mechanism a fluid-driven crack model triggered by ice cracking or hydraulic transients. The low quality factor values estimated are consistent with the resonance of an ice crack filled with water. This work shows that low frequency icequakes can be confusingly taken as volcanic LP events.
TL;DR: It has been concluded that the Costa Rican population is truly trihybrid, similar to populations in other Latin American countries; however, it differs from them fundamentally by the proportion of gene flow from ancestral populations.
Abstract: The general population of Costa Rica has sometimes been considered to be the product of an amalgamation of groups of diverse origin. To determine the magnitude of accumulated admixture since Spanish colonization, 11 classic genetic markers were analyzed in a total of 2196 individuals originating from five distinct regions of the country. A maximum likelihood approach was used. The proportions of genes of European, Amerindian and African ancestry were found to be 61%, 30% and 9% of the total population, respectively. Variation was observed at a regional level, with an increased European influence in the North (66%) and Central (65%) regions. Meanwhile an increase in Amerindian ancestry was found in the South (38%), and a higher incidence in the contribution of African genes was detected in the coastal regions (13% in the Atlantic and 14% in the North Pacific). A principal component (PC) analysis showed that 76% of the existing variability can be explained by the first two PCs, which is in agreement with the variations observed in the admixture process by geographic area. It has been concluded that the Costa Rican population is truly trihybrid, similar to populations in other Latin American countries; however, it differs from them fundamentally by the proportion of gene flow from ancestral populations.