Santiago Ospina Ramirez - Academia.edu (original) (raw)

Papers by Santiago Ospina Ramirez

Pharmaceuticals

Liposomes are widely used as delivery systems for therapeutic purposes. However, the toxicity ass... more Liposomes are widely used as delivery systems for therapeutic purposes. However, the toxicity associated with the multi-dose administration of these nanoparticles is not fully elucidated. Here, we evaluated the toxicity of the prolonged administration of liposomes composed of neutral or cationic phospholipids often used in drug and gene delivery. For that purpose, adult wild-type mice (C57Bl6) were randomly distributed into three groups receiving either vehicle (PBS), neutral, or cationic liposomes and subjected to repeated intravenous injections for a total of 10 doses administered over 3 weeks. Several parameters, including mortality, body weight, and glucose levels, were monitored throughout the trial. While these variables did not change in the group treated with neutral liposomes, the group treated with the positively charged liposomes displayed a mortality rate of 45% after 10 doses of administration. Additional urinalysis, blood tests, and behavioral assays to evaluate impair...

Este articulo presenta el resultado de la primera etapa de un proyecto de investigacion que esta ... more Este articulo presenta el resultado de la primera etapa de un proyecto de investigacion que esta siendo desarrollado por la Universidad Tecnologica de Pereira, destinado a determinar las estrategias de mantenimiento utilizadas por la industria del area metropolitana Pereira – Dosquebradas. Esta primera etapa aborda el estudio de la gran y mediana industria. Para alcanzar los resultados se realizo una segmentacion de la industria por tamano, se diseno y aplico un estudio estadistico en el segmento resenado y se obtuvo una cualificacion y cuantificacion del estado de la funcion Mantenimiento en dichos sectores. Se espera que los resultados sirvan de referencia a los gremios economicos de la region y a las industrias estudiadas, para el trazado de politicas frente a las falencias encontradas.

Cells, 2021

Traumatic brain injury (TBI) is a head injury that disrupts the normal brain structure and functi... more Traumatic brain injury (TBI) is a head injury that disrupts the normal brain structure and function. TBI has been extensively studied using various in vitro and in vivo models. Most of the studies have been done with rodent models, which may respond differently to TBI than human nerve cells. Taking advantage of the recent development of cerebral organoids (COs) derived from human induced pluripotent stem cells (iPSCs), which resemble the architecture of specific human brain regions, here, we adapted the controlled cortical impact (CCI) model to induce TBI in human COs as a novel in vitro platform. To adapt the CCI procedure into COs, we have developed a phantom brain matrix, matching the mechanical characteristics of the brain, altogether with an empty mouse skull as a platform to allow the use of the stereotactic CCI equipment on COs. After the CCI procedure, COs were histologically prepared to evaluate neurons and astrocyte populations using the microtubule-associated protein 2 (M...

Ecology letters, Nov 1, 2016

Theory predicts that both stabilising selection and diversifying selection jointly contribute to ... more Theory predicts that both stabilising selection and diversifying selection jointly contribute to the evolution of sexual signalling traits by (1) maintaining the integrity of communication signals within species and (2) promoting the diversification of traits among lineages. However, for many important signalling traits, little is known about whether these dynamics translate into predictable macroevolutionary signatures. Here, we test for macroevolutionary patterns consistent with sexual signalling theory in the perfume signals of neotropical orchid bees, a group well studied for their chemical sexual communication. Our results revealed both high species-specificity and elevated rates of evolution in perfume signals compared to nonsignalling traits. Perfume complexity was correlated with the number of congeners in a species' range, suggesting that perfume evolution may be tied to the remarkably high number of orchid bee species coexisting together in some neotropical communities...

Ecology and Evolution, 2015

Neotropical rainforests sustain some of the most diverse terrestrial communities on Earth. Euglos... more Neotropical rainforests sustain some of the most diverse terrestrial communities on Earth. Euglossine (or orchid) bees are a diverse lineage of insect pollinators distributed throughout the American tropics, where they provide pollination services to a staggering diversity of flowering plant taxa. Elucidating the seasonal patterns of phylogenetic assembly and functional trait diversity of bee communities can shed new light into the mechanisms that govern the assembly of bee pollinator communities and the potential effects of declining bee populations. Male euglossine bees collect, store, and accumulate odoriferous compounds (perfumes) to subsequently use during courtship display. Thus, synthetic chemical baits can be used to attract and monitor euglossine bee populations. We conducted monthly censuses of orchid bees in three sites in the Magdalena valley of Colombiaa region where Central and South American biotas convergeto investigate the structure, diversity, and assembly of euglossine bee communities through time in relation to seasonal climatic cycles. In particular, we tested the hypothesis that phylogenetic community structure and functional trait diversity changed in response to seasonal rainfall fluctuations. All communities exhibited strong to moderate phylogenetic clustering throughout the year, with few pronounced bursts of phylogenetic overdispersion that coincided with the transition from wet-to-dry seasons. Despite the heterogeneous distribution of functional traits (e.g., body size, body mass, and proboscis length) and the observed seasonal fluctuations in phylogenetic diversity, we found that functional trait diversity, evenness, and divergence remained constant during all seasons in all communities. However, similar to the pattern observed with phylogenetic diversity, functional trait richness fluctuated markedly with rainfall in all sites. These results emphasize the importance of considering seasonal fluctuations in community assembly and provide a glimpse to the potential effects that climatic alterations may have on both pollinator communities and the ecosystem services they provide.

Revista Colombiana de Anestesiología, 2011

La introducción del sugammadex en la práctica clínica podría mejorar el perfil de seguridad de lo... more La introducción del sugammadex en la práctica clínica podría mejorar el perfil de seguridad de los relajantes neuromusculares; sin embargo, su uso en pacientes con nefropatía es cuestionable, pues, en razón del mecanismo de eliminación del fármaco, este podría ser problemático. Este artículo se basa en un caso en el cual se administró sugammadex a una paciente con nefropatía, quien presentó rápida reversión de la relajación neuromuscular sin que se observaran efectos adversos.

Nature, 2007

Figure 1 | Holotype of Meliorchis caribea gen. et sp. nov. This orchid pollinarium, carried by a ... more Figure 1 | Holotype of Meliorchis caribea gen. et sp. nov. This orchid pollinarium, carried by a worker stingless bee (Proplebeia dominicana), is preserved in amber from the Dominican Republic and represents the first definitive fossil record for the family Orchidaceae. a, General view of encapsulated specimen (scale bar, 1,000 mm). b, Detailed view of the pollinia surface showing pollen units (scale bar, 50 mm).

Zoological Journal of the Linnean Society, 2011

In orchid bees, males signal their availability as mates by fanning 'perfumes', i.e. blends of vo... more In orchid bees, males signal their availability as mates by fanning 'perfumes', i.e. blends of volatiles that are collected from environmental sources and stored in hind leg pouches. The chemical composition of such perfumes in males with either two or three mandibular teeth has previously led to the discovery of two sympatric, cryptic lineages within Euglossa viridissima Friese on the Yucatan peninsula, Mexico. Here, we combine chemical, morphological, and genetic data for an integrated characterization of the two lineages. The lectotype of E. viridissima Friese in the Museum of Natural History in Vienna has two mandibular teeth, and the species name viridissima must thus be assigned to the predominantly bidentate lineage, whereas the completely tridentate lineage is described as a novel species, Euglossa dilemma sp. nov. Bembé & Eltz. Chemical profiling and microsatellite genotyping revealed that E. viridissima males can occasionally (~10% of individuals) express a third mandibular tooth, but this tooth is not positioned centrally on the mandible as in E. dilemma, but is displaced towards the tip. Thus, males of the two lineages can be unambiguously diagnosed by mandibular characters alone. Based on 889 bp of CO1 sequence data, we confirm that E. viridissima and E. dilemma constitute a monophyletic group within the genus Euglossa. However, CO1 alone failed to separate these two lineages due to the lack of parsimony-informative sites. Both species occur in broad sympatry across Central America, but the orchid bees recently introduced to Florida have three mandibular teeth in males, i.e. belong to E. dilemma.z oj_740 1064..1076

Science, 2011

Insect sensory biases played a major role in driving reproductive adaptations in flowering plants.

Plastic and Reconstructive Surgery, 2003

Molecular Phylogenetics and Evolution, 2010

Stingless bees (Meliponini) constitute a diverse group of highly eusocial insects that occur thro... more Stingless bees (Meliponini) constitute a diverse group of highly eusocial insects that occur throughout tropical regions around the world. The meliponine genus Melipona is restricted to the New World tropics and has over 50 described species. Melipona, like Apis, possesses the remarkable ability to use representational communication to indicate the location of foraging patches. Although Melipona has been the subject of numerous behavioral, ecological, and genetic studies, the evolutionary history of this genus remains largely unexplored. Here, we implement a multigene phylogenetic approach based on nuclear, mitochondrial, and ribosomal loci, coupled with molecular clock methods, to elucidate the phylogenetic relationships and antiquity of subgenera and species of Melipona. Our phylogenetic analysis resolves the relationship among subgenera and tends to agree with morphology-based classification hypotheses. Our molecular clock analysis indicates that the genus Melipona shared a most recent common ancestor at least $14-17 million years (My) ago. These results provide the groundwork for future comparative analyses aimed at understanding the evolution of complex communication mechanisms in eusocial Apidae.

Molecular Ecology, 2012

The Neotropical myrmecophytic tree Cordia alliodora hosts symbiotic Azteca ants in most of its wi... more The Neotropical myrmecophytic tree Cordia alliodora hosts symbiotic Azteca ants in most of its widespread range. The taxonomy of the genus Azteca is notoriously difficult, which has frequently obscured species identity in ecological studies. We used sequence data from one mitochondrial and four nuclear loci to infer phylogenetic relationships, patterns of geographic distribution, and timing of diversification for 182 colonies of five C. alliodora-dwelling Azteca species from Mexico to Colombia. All morphological species were recovered as monophyletic, but we identified at least five distinct genetic lineages within the most abundant and specialized species, Azteca pittieri. Mitochondrial and nuclear data were concordant at the species level, but not within species. Divergence time analyses estimated that C. alliodora-dwelling Azteca shared a common ancestor approximately 10-22 million years ago, prior to the proposed arrival of the host tree in Middle America. Diversification in A. pittieri occurred in the Pleistocene and was not correlated with geographic distance, which suggests limited historical gene flow among geographically restricted populations. This contrasts with the previously reported lack of phylogeographic structure at this spatial scale in the host tree. Climatic niches, and particularly precipitation-related variables, did not overlap between the sites occupied by northern and southern lineages of A. pittieri. Together, these results suggest that restricted gene flow among ant populations may facilitate local adaptation to environmental heterogeneity. Differences in population structure between the ants and their host trees may profoundly affect the evolutionary dynamics of this widespread ant-plant mutualism.

Microsurgery, 2004

Reports in the literature on the effectiveness of late-phase Ischemic preconditioning (IPC) in sk... more Reports in the literature on the effectiveness of late-phase Ischemic preconditioning (IPC) in skeletal muscle are controversial. The purpose of this study was to determine in the same muscle flap model the effectiveness of various IPC protocols in inducing late-phase protection. Rat latissimus dorsi muscle (LDM) flaps were preconditioned with either 30 or 60 min of total ischemia, divided as follows: single cycles of either 30 or 60 min, two cycles of 15 or 30 min, and three cycles of 10 or 20 min. Ischemia cycles were separated by 10 min of reperfusion. A day after IPC, flaps were elevated and challenged with 4 h of ischemia. Three days later, flaps were assessed for viability. We found that IPC protocols of different total durations and comprised of two or three cycles of ischemia elicited a protective effect against necrosis. We conclude that IPC induces late-phase protection against necrosis in skeletal muscle, and that the protection requires more than one ischemia/reperfusion cycle.

Journal of Chemical Ecology, 2012

Here, we describe a novel method for the extraction of insect cuticular hydrocarbons using silica... more Here, we describe a novel method for the extraction of insect cuticular hydrocarbons using silica gel, herein referred to as "silica-rubbing". This method permits the selective sampling of external hydrocarbons from insect cuticle surfaces for subsequent analysis using gas chromatography-mass spectrometry (GC-MS). The cuticular hydrocarbons are first adsorbed to silica gel particles by rubbing the cuticle of insect specimens with the materials, and then are subsequently eluted using organic solvents. We compared the cuticular hydrocarbon profiles that resulted from extractions using silica-rubbing and solvent-soaking methods in four ant and one bee species: Linepithema humile, Azteca instabilis, Camponotus floridanus, Pogonomyrmex barbatus (Hymenoptera: Formicidae), and Euglossa dilemma (Hymenoptera: Apidae). We also compared the hydrocarbon profiles of Euglossa dilemma obtained via silica-rubbing and solid phase microextraction (SPME). Comparison of hydrocarbon profiles obtained by different extraction methods indicates that silica rubbing selectively extracts the hydrocarbons that are present on the surface of the cuticular wax layer, without extracting hydrocarbons from internal glands and tissues. Due to its surface specificity, efficiency, and low cost, this new method may be useful for studying the biology of insect cuticular hydrocarbons.

Journal of Chemical Ecology, 2010

Male orchid bees collect volatiles, from both floral and non-floral sources, that they expose as ... more Male orchid bees collect volatiles, from both floral and non-floral sources, that they expose as pheromone analogues (perfumes) during courtship display. The chemical profile of these perfumes, which includes terpenes and aromatic compounds, is both species-specific and divergent among closely related lineages. Thus, fragrance composition is thought to play an important role in prezygotic reproductive isolation in euglossine bees. However, because orchid bees acquire fragrances entirely from exogenous sources, the chemical composition of male perfumes is prone to variation due to environmental heterogeneity across habitats. We used Gas Chromatography/Mass Spectrometry (GC/MS) to characterize the perfumes of 114 individuals of the green orchid bee (Euglossa aff. viridissima) sampled from five native populations in Mesoamerica and two naturalized populations in the southeastern United States. We recorded a total of 292 fragrance compounds from hind-leg extracts, and found that overall perfume composition was different for each population. We detected a pronounced chemical dissimilarity between native (Mesoamerica) and naturalized (U.S.) populations that was driven both by proportional differences of common compounds as well as the presence of a few chemicals unique to each population group. Despite these differences, our data also revealed remarkable qualitative consistency in the presence of several major fragrance compounds across distant populations from dissimilar habitats. In addition, we demonstrate that naturalized bees are attracted to and collect large quantities of triclopyr 2butoxyethyl ester, the active ingredient of several commercially available herbicides. By comparing incidence values and consistency indices across populations, we identify putative functional compounds that may play an important role in courtship signaling in this species of orchid bee.

Ecology, 2009

Male Neotropical orchid bees (Euglossini) collect volatile substances (fragrances) from flowers a... more Male Neotropical orchid bees (Euglossini) collect volatile substances (fragrances) from flowers and other sources (e.g., decaying wood) and store them in specialized hind tibial pockets. The accumulated chemicals are later emitted during courtship display, presumably to lure conspecific females for mating. We analyzed tibial fragrances of males of 15 sympatric Panamanian species in the genus Euglossa to test whether communities of euglossine bees are chemically structured, and to elucidate whether male fragrance signals evolve to convey premating isolation. Our analysis revealed substantial chemical disparity among all lineages. Disparity was mediated by compounds that were exclusive to certain species but also by differences in relative quantity of shared compounds. We mapped tibial fragrance compounds present in each species on a DNA-based phylogeny (reconstructed using partial sequences of COI, EF1-a, ArgK, and Pol-II) and found that most dominant compounds were highly homoplasious. In an analysis of chemical differentiation in relation to phylogenetic divergence through time, disparity was greater than expected from a null model at any point during evolutionary history, suggesting that diversifying selection has shaped fragrance phenotypes. Notably, chemical disparity was greater within recently diverged lineages than among them, suggesting that chemical preferences in orchid bees evolved rapidly in the early stages of species divergence. We postulate communication interference as the possible mechanism behind the observed fragrance differentiation, which may be the product of reproductive character (fragrance) displacement. Our findings are consistent with the hypothesis that male fragrance signals evolve to convey premating isolation.

Conservation Genetics Resources, 2010

We describe and characterize eight polymorphic microsatellite loci for the orchid bee species Eul... more We describe and characterize eight polymorphic microsatellite loci for the orchid bee species Eulaema meriana, an abundant species and important pollinator in wet lowland forests in tropical America. We also tested the cross-species amplification of these microsatellite loci in seven other species of the genus Eulaema. For E. meriana, number of alleles per locus ranged from four to nine and expected heterozygosity ranged from 0.377 to 0.854. Seven out of the eight loci described amplified in all seven other Eulaema species. These microsatellite loci will be of practical use for population structure, mating system and inbreeding studies in euglossine bees.

Biological Journal of the Linnean Society, 2010

The orchid bees constitute a clade of prominent insect pollinators distributed throughout the Neo... more The orchid bees constitute a clade of prominent insect pollinators distributed throughout the Neotropical region. Males of all species collect fragrances from natural sources, including flowers, decaying vegetation and fungi, and store them in specialized leg pockets to later expose during courtship display. In addition, orchid bees provide pollination services to a diverse array of Neotropical angiosperms when foraging for food and nesting materials. However, despite their ecological importance, little is known about the evolutionary history of orchid bees. Here, we present a comprehensive molecular phylogenetic analysis based on~4.0 kb of DNA from four loci [cytochrome oxidase (CO1), elongation factor 1-a (EF1-a), arginine kinase (ArgK) and RNA polymerase II (Pol-II)] across the entire tribe Euglossini, including all five genera, eight subgenera and 126 of the approximately 200 known species. We investigated lineage diversification using fossil-calibrated molecular clocks and the evolution of morphological traits using disparity-through-time plots. In addition, we inferred past biogeographical events by implementing model-based likelihood methods. Our dataset supports a new view on generic relationships and indicates that the cleptoparasitic genus Exaerete is sister to the remaining orchid bee genera. Our divergence time estimates indicate that extant orchid bee lineages shared a most recent common ancestor at 27-42 Mya. In addition, our analysis of morphology shows that tongue length and body size experienced rapid disparity bursts that coincide with the origin of diverse genera (Euglossa and Eufriesea). Finally, our analysis of historical biogeography indicates that early diversification episodes shared a history on both sides of Mesoamerica, where orchid bees dispersed across the Caribbean, and through a Panamanian connection, thus reinforcing the hypothesis that recent geological events (e.g. the formation of the isthmus of Panama) contributed to the diversification of the rich Neotropical biota.

Behavioral Ecology and Sociobiology, 2003

Social bees can deposit specialized glandular secretions, or signals, that allow foragers to revi... more Social bees can deposit specialized glandular secretions, or signals, that allow foragers to revisit rewarding and to avoid unrewarding food sources. However, it is not known if bees can orient towards olfactory cues such as excreta deposited near food sources. We report that Melipona mandacaia foragers (stingless bees) deposit an odor cue, anal droplets, and a previously undescribed ventro-abdominal odor on food sources. Surprisingly, foragers deposited attractive odor marks on good food sources to which they recruited and on poor food sources to which they did not recruit. Foragers left the most anal droplets on dilute food sources to which they did not recruit (1.25-M sucrose solution), yet returning foragers were attracted to anal droplets obtained on poor food sources and presented in bioassays. Foragers were attracted to ventro-abdominal odors obtained on good food sources (2.5-M sucrose solution). Chemical extractions suggest that odor marks contain attractive polar compounds. We also provide the first detailed description of forager waggling and spinning behavior on poor and good food sources. Waggling may be a method of dispersing anal droplets and spinning may help foragers learn local landmarks.

Animal Behaviour, 2003

We evaluated the ability of two Brazilian stingless bee species, Melipona mandacaia and M. bicolo... more We evaluated the ability of two Brazilian stingless bee species, Melipona mandacaia and M. bicolor, to recruit nestmates to a specific three-dimensional location. We used experimental feeder arrays and provide the first detailed evidence demonstrating that recruitment communication in Melipona can lead to large, rapid and highly significant increases in the number of nestmates visiting a specific location. Melipona bicolor and M. mandacaia foragers both recruited nestmates to the correct distance and direction, but differed in their ability to recruit nestmates to the correct height. These differences may relate to their respective habitats. Melipona mandacaia inhabits semi-arid areas of Caatinga where most food sources occur close to the ground, and its foragers evidently cannot recruit nestmates to the correct height. Melipona bicolor, an Atlantic rainforest species, evidently does not communicate height when the food source is at ground level, but can communicate height when the food source is at the forest canopy level (12 m high), where major food sources occur. Species-specific variation in three-dimensional location communication is intriguing because it suggests that Melipona may be a good model for studying the evolution of recruitment communication systems in highly social bees.