Showing papers by "University of Costa Rica published in 1998"
TL;DR: The morphological details of coupling between males and females in several species clearly indicated that selection favoring mechanical fit is not responsible for these trends.
Abstract: Hypotheses regarding the function of elaborate male genitalia were tested in a sample of insects and spiders by comparing their allometric values (slopes in log-log regressions on indicators of body size) with those of other body parts. Male genitalia consistently had lower slopes than other body parts. Perhaps as a consequence of this pattern, genitalic size also tended, though less consistently, to have lower coefficients of variation than did the size of other body parts. The morphological details of coupling between males and females in several species clearly indicated that selection favoring mechanical fit is not responsible for these trends. Sexual selection on male courtship structures that are brought into contact with females in precise ways may favor relatively low allometric values, in contrast to the high values seen in the other sexually selected characters (usually visual display devices) that have been studied previously, because a female's own size will influence her perception of the contact courtship devices of a male.
382 citations
TL;DR: In this article, a series of tests were performed by means of an automated hollow cylindrical torsional shear apparatus on undrained monotonic loading triaxial compression and extension tests on Toyoura sand.
354 citations
TL;DR: A positive correlation between degree of divergence (measured as Nei's genetic distance, D) and degree of postzygotic isolation is found and in anurans, hybrid sterility appears to evolve more quickly than inviability, which is consistent with the conclusions that involved Drosophila species.
Abstract: From literature data on 116 taxa crosses involving 46 species of frogs, we found a positive correlation between degree of divergence (measured as Nei's genetic distance, D) and degree of postzygotic isolation. In anurans, hybrid sterility appears to evolve more quickly than inviability, which is consistent with the conclusions of other studies that involved Drosophila species. The lower threshold of D = 0.30 for evolution of hybrid inviability that we found is similar to that observed for Drosophila. This consistency suggests that there may be a general pattern in the acquisition of reproductive isolation in animals.
234 citations
TL;DR: Despite differences in their pharmacokinetic profiles, equine whole IgG and F(ab')2 antivenoms show similar efficacy in the neutralization of edema, hemorrhage and myonecrosis induced by B. asper venom, suggesting that the use of antivenom made of antibody fragments may not improveneutralization of these effects.
170 citations
TL;DR: Bacterial LPS chimeras indicated that LPS is a relevant target for myotoxin II-(115-129)-peptide, which represents a group-II PLA2 with a direct bactericidal effect that is independent of an intrinsic enzymatic activity, but adscribed to the presence of a short cluster of basic/hydrophobic amino acids near its C-terminal loop.
Abstract: Mammalian group-II phospholipases A2 (PLA2) of inflammatory fluids display bactericidal properties, which are dependent on their enzymatic activity. This study shows that myotoxins II (Lys49) and III (Asp49), two group-II PLA2 isoforms from the venom of Bothrops asper, are lethal to a broad spectrum of bacteria. Since the catalytically inactive Lys49 myotoxin II isoform has similar bactericidal effects to its catalytically active Asp49 counterpart, a bactericidal mechanism that is independent of an intrinsic PLA2 activity is demonstrated. Moreover, a synthetic 13-residue peptide of myotoxin II, comprising residues 115−129 (common numbering system) near the C-terminal loop, reproduced the bactericidal effect of the intact protein. Following exposure to the peptide or the protein, accelerated uptake of the hydrophobic probe N-phenyl-N-naphthylamine was observed in susceptible but not in resistant bacteria, indicating that the lethal effect was initiated on the bacterial membrane. The outer membrane, isolated lipopolysaccharide (LPS), and lipid A of susceptible bacteria showed higher binding to the myotoxin II-(115−129)-peptide than the corresponding moieties of resistant strains. Bacterial LPS chimeras indicated that LPS is a relevant target for myotoxin II-(115−129)-peptide. When heterologous LPS of the resistant strain was present in the context of susceptible bacteria, the chimera became resistant, and vice versa. Myotoxin II represents a group-II PLA2 with a direct bactericidal effect that is independent of an intrinsic enzymatic activity, but adscribed to the presence of a short cluster of basic/hydrophobic amino acids near its C-terminal loop.
166 citations
TL;DR: In this article, a thorough, physicist's account of the formulation of the Standard Model (SM) of particle physics within the framework of non-commutative differential geometry (NCG) is given.
148 citations
TL;DR: In this article, the authors used the experience of Costa Rica during the last forty years to illustrate what the main issues are, discuss the history of deforestation in that country, and present results from conventional regression methods and from the application of spatial analyses.
Abstract: This paper addresses a central debate in research and policy on population and environment, namely the extent to which rapid population growth is associated with the massive deforestation currently underway in the tropics. We utilize the experience of Costa Rica during the last forty years to illustrate what the main issues are, discuss the history of deforestation in that country, and present results from conventional regression methods and from the application of spatial analyses. These analyses enable us to estimate the magnitude of the relation between population and deforestation and to identify the factors that are responsible for the linkage between them.
137 citations
Journal Article•
TL;DR: It is suggested that BaP1, and probably endogenous matrix metalloproteinases, degrade some protein components at the dermal-epidermal junction, inducing the formation of blisters.
Abstract: Blister formation and skin damage can be induced by BaP1, a haemorrhagic metalloproteinase from the venom of the snake Bothrops asper. Pathological changes in the skin were investigated after intramuscular injections of Bothrops asper haemorrhagic metalloproteinase BaP1. Blisters developed within the first hour, with separation of epidermis from the dermal-epidermal junction, whereas acantholysis of epithelial cells was not observed. After the third hour there was ulceration with formation of a proteinaceous scab and inflammatory infiltrate. By 7 to 14 days there was evidence of a regenerative process in dermis and epidermis. Haemorrhage occurred in both dermis and hypodermis as a consequence of BaP1 injection, together with damage of sebaceous glands and an inflammatory reaction in which enlarged macrophages were the predominant cell type. Zymography assays showed the presence of several endogenous metalloproteinases in the exudate, skin homogenates and plasma. In addition, BaP1 was detected in exudates and plasma by immunoblotting. This technique also demonstrated the presence of components immunologically related to laminin and collagen type IV in exudates. It is suggested that BaP1, and probably endogenous matrix metalloproteinases, degrade some protein components at the dermal-epidermal junction, inducing the formation of blisters.
117 citations
110 citations
TL;DR: In this paper, the link between chirality in the fermion sector and (anti-)self-duality of the boson sector is reexamined in the light of Connes' noncommutative geometry approach to the Standard Model.
79 citations
TL;DR: A practical and efficient gene transfer system for indica rice utilizing mature-seed derived explants and a simple bombardment device which uses compressed helium for accelerating DNA-coated metal particles and does not require vacuum.
Abstract: We developed a practical and efficient gene transfer system for indica rice utilizing mature-seed derived explants and a simple bombardment device which uses compressed helium for accelerating DNA-coated metal particles. Unlike instruments which have been described in the literature previously, this new bombardment device, which is an improvement of the particle inflow concept, does not require vacuum. This attribute simplifies the transformation procedure significantly and it makes rice transformation technology accessible to laboratories which may not have the resources to invest in more expensive particle bombardment instruments. We determined experimentally that we could recover transgenic rice plants utilizing three different particle bombardment instruments at comparable frequencies.
TL;DR: These myotoxins are important edema-forming components of B. asper venom, enzymatic activity is not a strict requirement to exert this effect, although in the case of myotoxin III it contributes to its development, and several inflammatory mediators participate in mouse foot pad edema induced by these myOToxins.
TL;DR: It is concluded that heritable variation in male courtship behavior has persisted in a wild population despite its overall relatively low genetic variability, and that genetic changes in mass-reared strains have altered the range of faculta...
Abstract: The evolutionary effects of crowding on male courtship behavior were studied using wild and mass-reared medflies. Mass-reared strains had been raised under highly crowded conditions in mass-rearing facilities for approximately 75, 180, and 238 generations. Pre-mounting courtship was facultatively shortened in both wild and mass-reared males under conditions of greater crowding. The courtship behavior of males of mass-reared strains was also shorter than that of wild males under similar conditions of crowding. Shorter courtships are probably advantageous for males in crowded conditions because they reduce the likelihood of the courtship being interrupted by other flies. Several types of data indicated that males rather than females were responsible for shortened courtships. We conclude that heritable variation in male courtship behavior has persisted in a wild population despite its overall relatively low genetic variability, and that genetic changes in mass-reared strains have altered the range of faculta...
TL;DR: The diniobium tetragonal lantern compound Nb2(hpp)4, 1, has been prepared in high yields by the reaction of NbCl3(DME), DME = dimethoxyethane, with a mixture of lithium naphthalenide and Li (hpp), hpp = the anion of 1,3,4,6,7,8-hexahydropyrimido[1,2-a]pyrimidine as mentioned in this paper.
Abstract: The diniobium tetragonal lantern compound Nb2(hpp)4, 1, has been prepared in high yields by the reaction of NbCl3(DME), DME = dimethoxyethane, with a mixture of lithium naphthalenide and Li(hpp), hpp = the anion of 1,3,4,6,7,8-hexahydropyrimido[1,2-a]pyrimidine. Compound 1 interacts with two equivalents of NaEt3BH to give the bis-adduct, 1·2NaEt3BH. In a refluxing mixture of THF/toluene, 1·2NaEt3BH loses one NaEt3BH molecule to give 1·NaEt3BH. Both adducts contain short Na to N−C−N “pseudo-allylic” interactions to the coordinated hpp ligand. Very little variation can be seen in the Nb−Nb bond distances, which are 2.2035(9), 2.2064(3), and 2.2187(7) A for 1, 1·2NaEt3BH and 1·NaEt3BH, respectively. By a synthetic route similar to that used to make 1, Nb2(azin)4·2LiCl·4THF, 2, was prepared using the anion of 7-azaindole; the Cl- ions are loosely coordinated to the Nb atoms. This ligand tends to give long metal−metal distances, and the Nb−Nb distance of 2.278(2) A is 0.07 A longer than that in 1.
TL;DR: It is demonstrated that the overall antigenic structure of region 115-129 is conserved among class II myotoxic phospholipases A2, despite differences in their corresponding amino acid sequences.
TL;DR: A series of complexes composed of three chromium atoms linearly arranged and surrounded by four dipyridyl amido anions, dpa, of the type [Cr3(dpa)4]n+, n=2, 3, have been prepared as discussed by the authors.
TL;DR: Southern blot analysis and enzymatic assays in primary transformants and progeny confirmed the stable integration and expression of introduced transgenes in all engineered cultivars.
TL;DR: Inhibition of snake venom protease activity by the addition of exogenous citrate was obtained using azure blue hide powder and azocasein as substrates and Trypsin was not inhibited in this system.
TL;DR: In this paper, several cobalt compounds that contain 2,2′-dipyridylamine (Hdpa) and its ionic forms, dpa− and H2dpa+ were characterized with the aim of structurally characterizing various coordination modes of such species.
TL;DR: In this article, the authors present data on the economic importance of the pesticide industry and describe the situation of acute poisonings from exposure to pesticides and consumption of contaminated foods, highlighting the need to reduce pesticide use.
Abstract: The use of pesticides has produced great agricultural benefits and, at the same time, serious public health problems that need to be solved. According to studies performed in the 1980s and 1990s, every year about half a million to one and a half million cases of acute pesticide poisoning are notified, together with 3,000 to 28,000 deaths. The purpose of this study was to draw attention to the incidence of acute pesticide poisoning and to the social and economic costs that are attributable to pesticides in different parts of the world. We present data on the economic importance of the pesticide industry and describe the situation of acute poisonings from exposure to pesticides and consumption of contaminated foods. Such data show that pesticide poisonings are more frequent in developing countries than in industrialized countries, even though developing countries consume less pesticides. We also estimate the economic costs of pesticide poisonings and examine certain other aspects of the situation, underscoring the need to reduce pesticide use.
TL;DR: The study focuses on the function of a pointed and upward projecting (‘pup’) apophysis on the male pedipalpal femur: it engages an indentation in the genital bulb during copulation.
Abstract: Genital mechanics are studied in five species from three genera of neotropical pholcid spiders. The study focuses on the function of a pointed and upward projecting (‘pup’) apophysis on the male pedipalpal femur: it engages an indentation in the genital bulb during copulation. This character is geographically restricted to spiders in Central and North America and the West Indies and is considered a key character of the monophyletic ‘Modisimus group’. This includes the genera Modisimus Simon, 1893, Psilochorus Simon, 1893, Bryantina Brignoli, 1985, Anopsicus Chamberlin & Ivie, 1938, and some species now misplaced in Coryssocnemis Simon, 1893 and Blechroscelis Simon, 1893. Evidence for the polyphyly of the following genera is presented: Psilochorus, Coryssocnemis, and Blechroscelis. Some notes on the reproductive biology of the species studied are briefly presented.
TL;DR: In this article, a theory of summability for generalized functions of one real variable is presented, and the relationship between the average behaviour of generalized functions according to this summability theory and the distributional behaviour is studied.
Abstract: A theory of summability for generalized functions of one real variable is presented; this theory generalizes the classical theory of summability of series and integrals. The relationship between the average behaviour of generalized functions according to this summability theory and the distributional behaviour is studied. Several applications are given.
TL;DR: The results suggest that the early low-frequency hearing loss in this family is associated with endolymphatic hydrops, and elucidation of the role of the diaphanous gene in hearing will therefore lead to a better understanding of the mechanism of endoly mph hydrops.
Abstract: Background Autosomal dominant, nonsyndromic, hereditary hearing impairment in a large Costa Rican kindred is caused by a mutation in the human homolog of the Drosophila diaphanous gene. Objective To further characterize the phenotype of DFNA1 with comprehensive audiovestibular evaluation and computed tomography of the temporal bone. Patients One affected child and 2 affected adults of the Costa Rican kindred who harbor a mutation in the diaphanous gene. Setting Medical Center at the University of California, San Francisco. Intervention Otologic and neuro-otologic examination; pure tone audiometry, speech audiometry, and immitance testing; auditory evoked potentials, electrocochleography, and otoacoustic emissions; electronystagmography and vestibular autorotation tests; and computed tomography of the temporal bone. Results The youngest subject, an 8-year-old boy, had a mild hearing loss, intact stapedial reflexes, otoacoustic emissions at high frequencies, normal auditory evoked potentials, and electrocochleographic findings consistent with endolymphatic hydrops. The two adults had severe to profound bilateral sensorineural hearing impairment. Electronystagmography disclosed normal vestibular function. Computed tomography demonstrated normal external, middle, and inner ear structures. Conclusions These results suggest that the early low-frequency hearing loss in this family is associated with endolymphatic hydrops. Elucidation of the role of the diaphanous gene in hearing will therefore lead to a better understanding of the mechanism of endolymphatic hydrops.
TL;DR: Two tetranuclear complexes of the type [Mo2(DArF)3]2(μ-H)2, DArF = N,N'-diarylformamidinate, Ar = p-tolyl (1) and p-anisyl (2), have been prepared by reaction of Mo2(dArf)3Cl2 and NaHBEt3 as discussed by the authors.
Abstract: Two tetranuclear complexes of the type [Mo2(DArF)3]2(μ-H)2, DArF = N,N‘-diarylformamidinate, Ar = p-tolyl (1) and p-anisyl (2), have been prepared by reaction of Mo2(DArF)3Cl2 and NaHBEt3. The core...
TL;DR: In this article, two new types of products obtained by combining two dinuclear multiply metal−metal bonded species (doublets) to obtain cyclic tetranuclear products (quartets) are reported.
Abstract: New types of products obtained by combining two dinuclear multiply metal−metal bonded species (doublets) to obtain cyclic tetranuclear products (quartets) are reported. One new type consists of pairs of quadruply bonded Mo24+ units united by two μ-X links (X = H, OH, O) although in the last case oxidation has also occurred so that these are Mo25+ moieties. In these cases, the subunits are Mo2(DArF)3. The second new type consists of Mo2(DArF)2 subunits linked by four μ-X bridges, where X = Cl, Br, I. The previously known compound Mo4I8(PBun3)4 has been shown to differ from all previously known Mo4X8(PR3)4 molecules (X = Cl, Br) by retaining two quadruple bonds instead of being a metallacyclobutadiyne, as are the others.
TL;DR: It is shown that a cellular UDP-glucose deficiency causes hypersensitivity to the cytotoxic effect of this phospholipase, and experiments with genetically engineered C. perfringens PLC variants showed that the sphingomyelinase activity and the C-domain are required for its cytot toxic effect in UDP- glucose-deficient cells.
TL;DR: Female tapping behavior may be a mechanism for choosing between males after copulation has begun and is higher in shorter copulations, which did not result in sperm transfer to the female.
Abstract: The remarkable behavior of female Ozophora baranowskii of lightly tapping the male with the hind legs during copulation was studied in relation to multiple copulations, copulation length, and sperm transfer. Multiple copulations did not affect female fecundity, fertility, or longevity. The incidence of tapping was higher in shorter copulations, which did not result in sperm transfer to the female. Female tapping behavior may be a mechanism for choosing between males after copulation has begun.
TL;DR: This study supports a simple and credible explanation for the illusion of mesenchymal disappearance in the neonatal middle ear, which occurs in different species, whether gestation is completed in an intrauterine or an extrauterine environment.
Abstract: Objective: The fate of embryonic middle ear mesenchyme from a postgestational infant ear has been speculative. Recently a volume analysis of human neonatal temporal bones demonstrated that embryonic mesenchyme disappeared by redistribution and thinning to surface a growing middle ear space. 1 If this model is accurate, interaction with amniotic fluid and the gestational environment should not influence mesenchymal behavior. Therefore an opossum marsupial model was compared with human data. Methods: The temporal bones of opossum pups (20 to 36 days of age) were sectioned for histologic analysis. Computations were made for the volume of the middle ear air cavity (VAC), volume of the bone cavity (VBC), volume of mesenchyme (VM), and percentage of the middle ear occupied by mesenchyme (%M), which were plotted against height using regression statistics. These data were compared with human neonatal (0 to 30 days of age) temporal bones. Results: In both the opossum and the human the VAC and the VBC increased in parallel with growth of the body. In the opossum the VAC and VBC both grew at 0.148 mm 3 /mm of body length. In humans, both the VAC and VBC grew 6.1 mm 3 /cm of body length. The VM in the opossum remained constant at 0.98 mm 3 , regardless of body length. In humans the VM remained constant at 71.7 mm 3 , regardless of body length. Therefore the %M proportionately decreased inversely with increasing ear size in both the opossum and the human neonate. Conclusion: This study supports a simple and credible explanation for the illusion of mesenchymal disappearance in the neonatal middle ear. The mesenchymal connective tissue redistributes to cover a larger surface area in a persistently enlarging cavity. These findings occur in different species, whether gestation is completed in an intrauterine or an extrauterine environment.
TL;DR: In this article, the anomalous behavior of the spin-spin correlation at large momentum transfer in elastic scattering is described in terms of the degrees of freedom associated with the onset of the charm threshold.
Abstract: The anomalous behavior of the spin-spin correlation at large momentum transfer in pp elastic scattering is described in terms of the degrees of freedom associated with the onset of the charm threshold. A non-perturbative analysis based on the symmetries of QCD is used to extract the relevant dynamics of the charmonium-proton interaction. The enhancement to pp amplitudes and their phase follow from analyticity and unitarity, giving a plausible ex
TL;DR: It is shown how to construct a strict, flabby quantization, which is moreover an asymptotic morphism and satisfies the reality and traciality constraints, on any oriented Riemannian manifold.
Abstract: We address one of the open problems in quantization theory recently listed by Rieffel. By developping in detail Connes' tangent groupoid principle and using previous work by Landsman, we show how to construct a strict, flabby quantization, which is moreover an asymptotic morphism and satisfies the reality and traciality constraints, on any oriented Riemannian manifold. That construction generalizes the standard Moyal rule. The paper can be considered as an introduction to quantization theory from Connes' point of view.