Showing papers by "University of Costa Rica published in 2001"
Journal Article•
[...]
626 citations
TL;DR: Contrary to previous reports, it is shown that parthenolide, like other SLs, inhibits NF-κB most probably by alkylating p65 at Cys38, and the amount of remaining IκB was too low to explain the observed NF-β degradation inhibition.
394 citations
TL;DR: In a recent workshop with 88 Latin American herpetologists and conservationists, a signed resolution was presented to better understand the geographic extent of amphibian population declines, their possible causes, and the measures needed to improve Latin American scientists' ability to research the phenomenon and make effective management recommendations as mentioned in this paper.
Abstract: Although dramatic amphibian population declines have been reported worldwide, our understanding of the extent of the declines in Latin America, where amphibian diversity is high, is limited to a few well-documented studies. To better understand the geographic extent of declines, their possible causes, and the measures needed to improve Latin American scientists' ability to research the phenomenon and make effective management recommendations, we convened three regional workshops with 88 Latin American herpetologists and conservationists. Population declines are widespread in Latin America. At least 13 countries have experienced declines, and in 40 cases species are now thought to be extinct or extirpated in a country where they once occurred. Declines or extinctions have affected 30 genera and nine families of amphibians. Most declines have occurred in remote highlands, above 500 m in elevation in Central America and above 1000 m in the Andes. Most documented declines occurred in the 1980s. Of the possible causes studied to date, climate change appears to be important at one site and chytrid fungal disease has been identified at sites in three countries. Although many monitoring studies are currently underway in a variety of habitats, most studies are recent and of short duration. In a signed resolution, workshop participants called for greater collaboration and communication among scientists working in Latin America to understand the geographic extent of population declines and the distribution of possible causal factors. In situ conservation is important to protect habitats, but captive-rearing programs for species subject to imminent extinction are also needed. Better understanding of the taxonomy and natural history of amphibians and more funding for research and monitoring are critical to developing a scientific basis for management action to arrest and reverse population declines.
388 citations
TL;DR: Twelve compounds containing two quadruply bonded Mo(2)(DAniF)(3) (DAnIF = N,N'-di-p-anisylformamidinate) units linked by dicarboxylate anions have been prepared in high purity and good yields.
Abstract: Twelve compounds containing two quadruply bonded Mo2(DAniF)3 (DAniF = N,N‘-di-p-anisylformamidinate) units linked by dicarboxylate anions have been prepared in high purity and good yields. All of these compounds have been characterized by crystallography and NMR. The dinuclear pairs display electrochemical behavior which is controlled by the nature of the bridging dicarboxylate group. As described by the linkers, the compounds are oxalate, 1; acetylene dicarboxylate, 2; fumarate, 3; tetrafluorophthalate, 4; carborane dicarboxylate, 5; ferrocene dicarboxylate, 6; malonate, 7; succinate, 8; propane-1,3-dicarboxylate, 9; tetrafluorosuccinate, 10; bicyclo[1.1.1]pentane-1,3-dicarboxylate, 11; and trans-1,4-cyclohexanedicarboxylate, 12.
131 citations
TL;DR: These observations unequivocally identify the sequence 115-129 (KKYKAYFKLKCKK) of the Lys49 PLA(2) of A. p.
121 citations
TL;DR: The polyphasic approach used to discern the molecular events leading to Brucella internalization provides new alternatives for exploring the complexity of the signals required by intracellular pathogens for cell invasion.
110 citations
TL;DR: Data suggest that the expression of episomal BSV observed during the in vitro procedure is correlated with the presence of an integrated form, similar to that observed during micropropagation of banana streak virus.
Abstract: Banana streak virus (BSV) is causing increasing concern in almost every producing area of banana and plantain (Musa spp.) worldwide. This situation appeared partially linked to some breeding lines and micropropagated hybrids. A complete BSV sequence integrated into the genome of a triploid plantain has been recently characterised and it has been hypothesised that it could give rise to infectious virus via recombination. In this study, we evaluated the effect of a routine micropropagation procedure on the expression of BSV in the FHIA 21 tetraploid hybrid. The widespread presence of integrated sequences and the absence of episomal BSV in thirty FHIA 21 “mother plants” selected for micropropagation were first confirmed by specific PCR and IC-PCR tests. The proliferation stage of the procedure, characterised by an intensive production of neoformed buds, appeared determinant in BSV expression whereas the rooting and acclimatisation stages had little or no effect. The duration in culture and the way of subdividing the clumps of proliferation influenced greatly the percentage of episomal BSV infections, reaching 58% of infected micropropagated lines after six in vitro subcultures. These data suggest that the expression of episomal BSV observed during the in vitro procedure is correlated with the presence of an integrated form.
107 citations
TL;DR: Results of NMR studies of all seven compounds are consistent with the presence of a highly symmetrical structure, and these compounds display a rich electrochemical behavior that is affected by the nature of the carboxylate group.
Abstract: Seven complexes obtained by reacting the quadruply bonded complex [Mo2(cis-DAniF)2(CH3CN)4](BF4)2 (DAniF = N,N'-di-p-anisylformamidinate) and (Bun4N+)2(Carb2-), where Carb2- is a dicarboxylate anion, have been found to have a ratio of dimetal unit to dicarboxylate of 1:1. As noted by the carboxylate linker, the compounds are oxalate, 1, fumarate, 2, ferrocene dicarboxylate, 3, 4,4'-biphenyldicarboxylate, 4, acetylenedicarboxylate, 5, tetrafluorophthalate, 6, and carborane dicarboxylate, 7. Structural characterization of 1-4 revealed a square of dimolybdenum units linked by the dicarboxylate anions, each having an interstice capable of accommodating specific solvent molecules. Results of NMR studies of all seven compounds are consistent with the presence of a highly symmetrical structure. These compounds display a rich electrochemical behavior that is affected by the nature of the carboxylate group.
105 citations
TL;DR: Analysis of structural changes by circular dichroism spectroscopy demonstrated significant changes in the secondary structure only in the case of N-terminal octapeptide cleavage, which indicates that Pr TX-I and PrTX-III possess regions other than the catalytic site, which determine their toxic and pharmacological activities.
99 citations
TL;DR: In this article, it was shown that the noncommutative spheres of Connes and Landi are quantum homogeneous spaces for certain compact quantum groups and that they support spin geometries.
Abstract: We show that the noncommutative spheres of Connes and Landi are quantum homogeneous spaces for certain compact quantum groups. We give a general construction of homogeneous spaces which support noncommutative spin geometries.
87 citations
TL;DR: Higher levels of free IAA and ABA were obtained in the embryogenic calli when compared to the non-embryogenic, while no differences were observed among callus types in the other hormones evaluated.
Abstract: Carrot (Daucus carota L. F1 hybrid Starca) excised hypocotyls were cultured on Murashige and Skoog medium with and without 2,4-dichlorophenoxy acetic acid (2,4-D) to determine the effect of this plant growth regulator on their further development and their endogenous hormone levels. Culture in the absence of 2,4-D stimulated root development at one end of the hypocotyl segments and increased the endogenous levels of free indole-3-acetic acid (IAA), zeatin/zeatin riboside and N6(Delta2-isopentenyl) adenine/N6(Delta2-isopentenyl) adenosine, as determined by radio-immunoassay. On the other hand, the presence of 2,4-D in the culture medium promoted callus induction and proliferation, together with abscisic acid (ABA) accumulation, in the hypocotyl segments during the first weeks of culture. When the callus segments generated in the hypocotyl sections cultured in the presence of 2,4-D were cultivated further, the development of two callus types was observed, one composed of preglobular and globular embryos and the other translucent, watery and lacking any sign of organisation. The embryos of the first type germinated when callus segments were transferred to regeneration conditions, while no change was observed when the second type was induced to regenerate. Higher levels of free IAA and ABA were obtained in the embryogenic calli when compared to the non-embryogenic, while no differences were observed among callus types in the other hormones evaluated. The possible role of the different plant hormones during induction of somatic embryogenesis is discussed.
TL;DR: The disease affecting the Costa Rican family constitutes an axonal, autosomal recessive CMT subtype (ARCMT2B), and the epithelial membrane protein 3 gene, encoding a PMP22 homologous protein and located on 19q13.3, was ruled out as being responsible for this form of CMT.
Abstract: Articulo cientifico -- Universidad de Costa Rica. Instituto de Investigaciones en Salud, 2001. Este documento es privado debido a limitaciones de derechos de autor.
TL;DR: It is argued that the mechanisms that regulate progeny vigor are disrupted in trees from pastures, as indicated by 12 of 16 indicators of plant vigor.
Abstract: We compared the rate of pollen deposition, the likelihood of fruit production, the number of seeds per fruit, the outcrossing rate, and the progeny vigor of the tropical dry forest tree Enterolobium cyclocarpum for individuals in pastures vs. individuals in continuous forest. We found that flowers from trees growing in continuous forests were more likely to have pollen deposited on their stigmas than flowers from trees in pastures (52.1 vs. 32.3%, respectively). We also found that trees from continuous forests were almost six times more likely to set fruits and produce more seeds per fruit than trees in pastures. Morever, progeny from trees in continuous forests were, on average, more vigorous than the progeny from trees in pastures, as indicated by 12 of 16 indicators of plant vigor. However, there was no significant difference in the multilocus estimate of the outcrossing rate between the two groups of trees (tm = 1.00 and 0.99 for trees from continuous forest and trees from pastures, respectively). But there are differences in the correlation of paternity between the progeny of the two groups, where the progeny from trees in pastures showed a lower correlation of paternity than progeny of trees from continuous forests (r(p) = 0.104 and r(p) = 0.189, respectively). We argue that the mechanisms that regulate progeny vigor are disrupted in trees from pastures. We discuss the implications of these findings for the conservation of E. cyclocarpum.
TL;DR: Reaction of [cis-Mo2(DAniF)2(CH3CN)4](BF4)2, DAn iF = N,N‘-di-p-anisylformamidinate, and (Bun4N)2 gives the first neutral molecular triangle derived from quadruply bonded dimolybdenum units.
Abstract: Reaction of [cis-Mo2(DAniF)2(CH3CN)4](BF4)2, DAniF = N,N‘-di-p-anisylformamidinate, and (Bun4N)2(trans-1,4-cyclohexanedicarboxylate) gives the first neutral molecular triangle derived from quadruply bonded dimolybdenum units.
TL;DR: Its design is based on the mass separation capabilities of a 90° cylindrical crossed electric and magnetic sector-field analyzer with a 2-cm radius, which under proper conditions is able to effectively cancel the angular and chromatic dispersion of the ion beam, thus improving the resolving power of the instrument.
TL;DR: The new 3-desoxyanthocyanidins 6,7,3'-trihydroxy-5,4'-dimethoxy-flavylium and 6, 7,3',4'-tetrahydroxy- 5-methoxy -flavolium and the known Carajurin were isolated by bioguided fractionation from the leaves of Arrabidaea chica, with transcription factor NF-kappaB as target.
TL;DR: It is demonstrated that fruit and seed production are directly related to the number of microgametophytes per pistil in natural populations of P. quinata.
Abstract: Several studies have demonstrated, using controlled pollinations, that the number and identity of pollen grains deposited onto a flower's stigma affect the reproductive success of plants. However, few studies have shown this relationship under conditions of natural pollination. Using the tropical dry forest tree Pachira quinata, we evaluated the relationship between the number of microgametophytes per pistil and the number of sires with respect to the production of fruits and seeds in a natural population of Pachira quinata. Our study demonstrates that fruit and seed production are directly related to the number of microgametophytes per pistil in natural populations of P. quinata. Only 6% of the marked flowers developed into mature fruits and 10% of the marked flowers initiated fruits but later aborted them. A mean of 23 pollen grains were required to produce a seed. Flowers with >400 pollen grains on the stigma always developed into mature fruits, whereas flowers that received <200 grains never matured fruits. Half of the pollen grains transferred to a flower stigma germinated and developed pollen tubes to the base of the style. The number of pollen grains on a stigma explained 34% of the variation in seed number per fruit, and the number of seeds produced per fruit is positively correlated with the size of the seeds. The population of P. quinata studied is predominantly outcrossing, and seeds within fruits are sired by one or a few donors. The total seed crop within trees was sired by three to five donors. Our study examined the implications of the variation in size of microgametophyte loads per pistil with respect to the breeding system and the paternity of progeny under natural conditions. The competitive ability of pollen and pollen tube attrition are important factors regulating fruit production in P. quinata.
TL;DR: In this article, six molecular squares were obtained by reacting the singly metal-metal-bonded complex [Rh2(cis-DAniF)2(CH3CNeq)4 (CH3CNax)2](BF4)2 (DANiF = N,N,N′-di-p-anisylformamidinate), and (Et4N+)2(Carb2−) where Carb2− represents the dicarboxylate anion bicyclo[1.1]
Abstract: Six molecular squares were obtained by reacting the singly metal–metal-bonded complex [Rh2(cis-DAniF)2(CH3CNeq)4(CH3CNax)2](BF4)2 (DAniF = N,N′-di-p-anisylformamidinate), and (Et4N+)2(Carb2−) where Carb2− represents the dicarboxylate anion bicyclo[1.1.1]pentane-1,3-dicarboxylate, 1; tetrafluoroterephthalate, 2; 1,4-cubanedicarboxylate, 3; terephthalate, 4; fumarate, 5; trans-1,4-cyclohexanedicarboxylate, 6; these squares stack in the crystal forming square channels capable of accommodating solvent molecules and the NMR spectra are consistent with the presence of highly symmetrical structures even in solution.
TL;DR: Data indicate that enzymatic activity is relevant for some pharmacological effects induced by crotoxin B (mainly lethal, myotoxic and anticoagulant activities), and also evidence that this subunit of crot toxin displays regions different from the active catalytic site which are involved in some of the toxic and pharmacological results induced by this phospholipase A(2).
TL;DR: It is concluded that neuwiedase, despite its lack of hemorrhagic effect when injected in the gastrocnemius muscle, contributes to local tissue damage by inducing edema, inflammatory infiltrate and mild myotoxicity, and by degrading extracellular matrix components.
TL;DR: It is suggested that reactive oxygen and nitrogen-derived species are involved in the pathogenesis of the local tissue damage characteristic of Bothrops sp envenomations.
TL;DR: There was a much higher accumulation of equine antibodies in muscle tissue that had been injected with B. asper venom than in non-envenomated tissue, indicating that venom-induced microvessel damage probably favors a prominent and similar extravasation of both IgG and F(ab')(2) antibodies.
TL;DR: The results suggest that hyperalgesia induced by Bothrops asper venom is, at least partially, mediated by bradykinin, phospholipase A(2) activity and leukotrienes.
TL;DR: Sixteen crystal structures have been determined for the Co3(dpa)(4)Cl2 (1) molecule in the following five crystalline solvates and magnetic susceptibility measurements indicate in each case that a gradual spin crossover, from a doublet to a quartet state, occurs over this temperature range.
Abstract: Sixteen crystal structures have been determined for the Co3(dpa)(4)Cl2 (1) molecule in the following five crystalline solvates: 1.0.85(C2H5)(2)O.0.15CH2Cl2 (at 120, 213, 296 K); 1.C(4)H(8)O (at 120, 295 K); 1.C(6)H(6) (at 170, 213, 260, 316 K); 1.C(6)H(12) (at 120, 213, 295 K); and 1.1.75C(7)H(8).0.5C(6)H(14) (at 90, 110, 170, 298 K). For 1.0.85(C(2)H(5))(2)O.0.15CH2Cl2 the molecule of 1 is almost symmetrical at 120 K (Co-Co distances of 2.3191(3) and 2.3304(3) A) and remains so at 296 K (2.2320(3) and 2.3667(4) A). For 1.C(4)H(8)O the Co(3) chain is precisely symmetric at both 120 and 295 K though the Co-Co distances increase from 2.3111(4) to 2.3484(4) A as the temperature rises. Compound 1.C(6)H(6) is isomorphous with 1.C(4)H(8)O at 213 and 295 K and has rigorously symmetrical molecules at these two temperatures. Between 213 and 120 K the space group changes from Pccn to P2(1)/c, so that a symmetrical arrangement is no longer required and the two Co-Co distances then differ slightly (by 0.013 A). For 1.C(6)H(6) there is a phase change between 316 K (Pca2(1)) and 260 K (Pna2(1)). At all four temperatures, however, the molecule is almost symmetrical, with the two independent Co-Co distances never differing by more than 0.026 A. 1.1.75C(7)H(8).0.5C(6)H(14) contains, at all temperatures between 90 and 298 K, two crystallographically independent molecules, each of which is distinctly unsymmetrical at 298 K (Co-Co distances of 2.312(2) and 2.442(2) A for one and 2.310(2) and 2.471(2) for the other). In the first of these the distances converge to a much smaller separation (0.056 A) at 90 K while in the second the difference decreases to only 0.006 A at 90 K. Magnetic susceptibility measurements from 1.8 to 350 K indicate in each case that a gradual spin crossover, from a doublet to a quartet state, occurs over this temperature range.
TL;DR: The isolation of a new platelet-aggregating protein, named as percetin, from the venom of B. asper, which induces thrombocytopenia in mice is described and it is suggested that aspercetIn, by reducing platelet numbers, may help to treat snake venoms.
Abstract: Thrombocytopenia occurs in a number of patients bitten by Bothrops asper, a species responsible for the majority of snakebites in Central America and southern Mexico. In this work we describe the isolation of a new platelet-aggregating protein, named aspercetin, from the venom of B. asper, which induces thrombocytopenia in mice. Isolation was carried out by a combination of ion-exchange chromatography on DEAE-Sepharose and affinity chromatography on Affi-Gel Blue. Aspercetin is a disulfide-linked heterodimer, with a pI of 4.5 and a molecular mass of 29,759 Da, detemined by MALDI-ESI mass spectrometry. N-terminal sequence shows homology with a number of venom proteins which belong to the C-type lectin family. Aspercetin has functional similarities with botrocetin, from B. jararaca venom, since it induces platelet aggregation only in the presence of plasma or purified von Willebrand factor. Aspercetin-mediated platelet aggregation results from the interaction of von Willebrand factor with platelet receptor GPIb. Aspercetin lacks anticoagulant effect and does not agglutinate erythrocytes, in contrast with other representatives of the C-type lectin family isolated from snake venoms. Moreover, aspercetin is not lethal, nor does it induce myonecrosis, hemorrhage and edema. When injected intravenously or intramuscularly in mice it induces a rapid, dose-dependent drop in platelet counts and prolongs the bleeding time, suggesting that it may play a role in the thrombocytopenia that develops in a number of B. asper envenomations. Moreover, mice injected intravenously with aspercetin and then receiving an intradermal injection of B. asper hemorrhagic metalloproteinase BaP1 develop a larger hemorrhagic lesion than mice receiving only BaP1. This suggests that aspercetin, by reducing platelet numbers, may contribute to the hemorrhagic effect characteristic of B. asper envenomations.
TL;DR: In this paper, the intrinsic and effective optical properties of light diffusing and absorbing materials consisting of anatase titania pigments hosted in an electrolyte medium were described and a multiple scattering approach was applied to compute average path-length parameters and forward-scattering ratios used in four-flux radiative transfer calculations.
TL;DR: Three new linear compounds of the type Co(3)(dpa)(4)X(2), where dpa is the anion of di(2-pyridyl)amine and X is NCS(-) (5), CN (6), and N(CN)(2)(-) (7), have been prepared, and their structures and magnetic behavior have been studied.
Abstract: Three new linear compounds of the type Co(3)(dpa)(4)X(2), where dpa is the anion of di(2-pyridyl)amine and X is NCS(-) (5), CN(-) (6), and N(CN)(2)(-) (7), have been prepared, and their structures and magnetic behavior have been studied. In all of them, including three different solvates of 5, the Co(3) chains are symmetrical with Co-Co distances of ca. 2.31-2.32 A. The appearance of four lines in the (1)H NMR spectra of the three compounds is also consistent with a symmetrical structure in solution. For all compounds, the magnetic behavior is quite similar with mu(eff) of ca. 1.9-2.0 micro(B) at temperatures between 1.8 and 200 K. As the temperature increases, the effective moments increase gradually, but since saturation is not reached, even at 400 K, the high-spin state cannot be assigned.
TL;DR: Four compounds consisting of molecular loops formed from two quadruply bonded Mo2(DAniF)2 (DAnoF = N,N'-di-p-anisylformamidinate) units linked by two dicarboxylate anions have been prepared in high purity and essentially quantitative yields.
Abstract: Four compounds consisting of molecular loops formed from two quadruply bonded Mo2(DAniF)2 (DAniF = N,N'-di-p-anisylformamidinate) units linked by two dicarboxylate anions have been prepared in high purity and essentially quantitative yields. These compounds have been characterized by crystallography and NMR spectroscopy and display electrochemical behavior dependent on the nature of the dicarboxylate anion. However, the electronic communication between the two Mo2(4+) units is not strong. As denoted by the dicarboxylate linkers, the compounds are malonate, 1, 1,4-phenylendiacetate, 2, homophthalate, 3, and trans-cyclopentane-1,2-dicarboxylate, 4.
Journal Article•
TL;DR: An inventory of the understory and canopy of 4 ha of lower montane cloud forest at Monteverde, Costa Rica, yielded 190 bryophyte species: 133 hepatics, 56 mosses and 1 homwort, which appeared that the percentage of Bryophytes restricted to the canopy may be the same in lowland and montane rain forests.
Abstract: An inventory of the understory and canopy of 4 ha oflower montane cloud forest at Monteverde, Costa Rica, yielded 190 bryophyte species: 133 hepatics, 56 mosses and 1 homwort. Thick branches of the lower canopy were by far the richest habitat in terms of number of species (99), trunks from 1m upwards had 65 species, lianas, shrubs, saplings, or living leaves in the understory had about 36-46 species each, and 16 species were found on rotten logs. The figures are illustrative of the great diversification of microhabitats of bryophytes in a tropical montane cloud forest. About 36% ofthe species, including more than half ofthe corticolous ones, occurred exclusively in the canopy. It appeared thatthe percentage ofbryophyte species restricted to the canopy may be the same in lowland and montane rain forests, in spite of the great differences in species abundance and composition in the two kinds of forest.
TL;DR: ThevirB10 homolog gene was the sole gene studied to be significantly expressed more often in cancer strains than in gastritis strains (P = 0.03), and the number of repeated sequences at the 3′ end of the cagA gene or the presence of tyrosine phosphorylation motifs and the clinical origin of the strains.
Abstract: The composition and in vitro expression of the cag pathogenicity island genes in a group of Helicobacter pylori strains obtained from patients suffering from chronic gastritis-associated dyspepsia (n 5 26) or gastric carcinoma (n 5 17) were analyzed. No significant difference in the distribution of the 10 studied regions was found between the cases and the controls. Nine strains did not harbor any of the selected regions: eight (30.8%) isolated from patients with gastritis only and one (5.9%) from a patient with gastric carcinoma. No association was found between the number of repeated sequences at the 3* end of the cagA gene or the presence of tyrosine phosphorylation motifs and the clinical origin of the strains. The virB10 homolog gene was the sole gene studied to be significantly expressed more often in cancer strains than in gastritis strains (P 5 0.03).