RESUMEN
Recent fossil discoveries in Western Amazonia revealed that two distinct anthropoid primate clades of African origin colonized South America near the Eocene/Oligocene transition (ca. 34 Ma). Here, we describe a diminutive fossil primate from Brazilian Amazonia and suggest that, surprisingly, a third clade of anthropoids was involved in the Paleogene colonization of South America by primates. This new taxon, Ashaninkacebus simpsoni gen. et sp. nov., has strong dental affinities with Asian African stem anthropoids: the Eosimiiformes. Morphology-based phylogenetic analyses of early Old World anthropoids and extinct and extant New World monkeys (platyrrhines) support relationships of both Ashaninkacebus and Amamria (late middle Eocene, North Africa) to the South Asian Eosimiidae. Afro-Arabia, then a mega island, played the role of a biogeographic stopover between South Asia and South America for anthropoid primates and hystricognathous rodents. The earliest primates from South America bear little adaptive resemblance to later Oligocene-early Miocene platyrrhine monkeys, and the scarcity of available paleontological data precludes elucidating firmly their affinities with or within Platyrrhini. Nonetheless, these data shed light on some of their life history traits, revealing a particularly small body size and a diet consisting primarily of insects and possibly fruit, which would have increased their chances of survival on a natural floating island during this extraordinary over-water trip to South America from Africa. Divergence-time estimates between Old and New World taxa indicate that the transatlantic dispersal(s) could source in the intense flooding events associated with the late middle Eocene climatic optimum (ca. 40.5 Ma) in Western Africa.
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Cebidae , Platirrinos , Animales , Filogenia , Brasil , Haplorrinos , Fósiles , Roedores , Evolución BiológicaRESUMEN
Recently, the morphology and encephalization of the brain endocast of the Triassic non-mammaliaform probainognathian cynodont Riograndia guaibensis were studied. Here, we analyzed the brain endocast of an additional specimen of this species. The new endocast shows well-defined olfactory bulbs and a median sulcus dividing the hemispheres, traits that were not clearly observed in the first studied specimen. Encephalization quotients were also calculated, revealing similar values to other non-mammaliaform cynodonts and lower than those of the first analyzed specimen. The analyzed cranium is slightly larger than the first studied one and may represent an advanced ontogenetic stage. Hence, these differences may be related to the intraspecific variation of this cynodont or alternatively, to the preservation of each specimen.
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Fósiles , Cráneo , Evolución Biológica , Encéfalo , Fenotipo , Filogenia , Cráneo/anatomía & histologíaRESUMEN
An antimicrobial supramolecular assembly (ASA) is conspicuous in biomedical applications. Among the alternatives to overcome microbial resistance to antibiotics and drugs, ASAs, including antimicrobial peptides (AMPs) and polymers (APs), provide formulations with optimal antimicrobial activity and acceptable toxicity. AMPs and APs have been delivered by a variety of carriers such as nanoparticles, coatings, multilayers, hydrogels, liposomes, nanodisks, lyotropic lipid phases, nanostructured lipid carriers, etc. They have similar mechanisms of action involving adsorption to the cell wall, penetration across the cell membrane, and microbe lysis. APs, however, offer the advantage of cheap synthetic procedures, chemical stability, and improved adsorption (due to multipoint attachment to microbes), as compared to the expensive synthetic routes, poor yield, and subpar in vivo stability seen in AMPs. We review recent advances in polymer-based antimicrobial assemblies involving AMPs and APs.
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Antiinfecciosos/química , Polímeros/química , Animales , Péptidos Catiónicos Antimicrobianos/química , Membrana Celular/química , Pared Celular/química , Humanos , Nanoestructuras/químicaRESUMEN
The non-dinosaurian dinosauriform silesaurids are the closest relatives of crown-group dinosaurs and are thus, important for understanding the origins of that group. Here, we describe the limb bone histology of the Late Triassic silesaurid Sacisaurus agudoensis from the Candelária Sequence of the Santa Maria Supersequence, Rio Grande do Sul state, Brazil. The sampled bones comprise eight femora and one fibula from different individuals. The microscopic analysis of all elements reveals uninterrupted fibrolamellar bone tissue indicating rapid growth. A transition to slower growing peripheral parallel-fibered bone tissue in some individuals indicates a decrease in growth rate, suggesting ontogenetic variation within the sample. The osteohistology of Sacisaurus agudoensis is similar to that of other silesaurids and supports previous hypotheses that rapid growth was attained early in the dinosauromorph lineage. However, silesaurids lack the complex vascular arrangements seen in saurischian dinosaurs. Instead, they exhibit predominantly longitudinally-oriented primary osteons with few or no anastomoses, similar to those of some small early ornithischian dinosaurs. This simpler vascular pattern is common to all silesaurids studied to date and indicates relatively slower growth rates compared to most Dinosauria.
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Huesos/anatomía & histología , Dinosaurios/anatomía & histología , Fósiles/anatomía & histología , Animales , Evolución Biológica , Dinosaurios/crecimiento & desarrollo , Fémur/anatomía & histología , Tibia/anatomía & histologíaRESUMEN
Hybrid and antimicrobial nanoparticles (NPs) of poly (methyl methacrylate) (PMMA) in the presence of poly (diallyl dimethyl ammonium) chloride (PDDA) were previously obtained by emulsion polymerization in absence of surfactant with low conversion. In the presence of amphiphiles such as cetyl trimethyl ammonium bromide (CTAB), dioctadecyl dimethyl ammonium bromide (DODAB) or soybean lecithin, we found that conversion increased substantially. In this work, the effect of the amphiphiles on the NPs core-shell structure and on the antimicrobial activity of the NPs was evaluated. NPs dispersions casted on silicon wafers, glass coverslips or polystyrene substrates were also used to obtain antimicrobial coatings. Methods for characterizing the dispersions and coatings were based on scanning electron microscopy, dynamic light scattering, determination of thickness, rugosity, and wettability for the coatings and determination of colony-forming unities (log CFU/mL) of microbia after 1 h interaction with the coatings or dispersions. The amphiphiles used during PMMA/PDDA/amphiphile NPs synthesis reduced the thickness of the NPs PDDA shell surrounding each particle. The antimicrobial activity of the dispersions and coatings were due to PDDA-the amphiphiles were either washed out by dialysis or remained in the PMMA polymeric core of the NPs. The most active NPs and coatings were those of PMMA/PDDA/CTAB-the corresponding coatings showed the highest rugosity and total surface area to interact with the microbes. The dispersions and coatings obtained by casting of the NPs dispersions onto silicon wafers were hydrophilic and exhibited microbicidal activity against Escherichia coli, Staphylococcus aureus, and Candida albicans. In addition, a major effect of reduction in particle size revealed the suitability of nanometric and cationic NPs (sizes below 100 nm) represented by PMMA/PDDA/CTAB NPs to yield maximal microbicidal activity from films and dispersions against all microbia tested. The reduction of cell viability by coatings and dispersions amounted to 6-8 logs from [PDDA] ≥ minimal microbicidal concentration.
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Compuestos Alílicos/química , Antibacterianos/química , Antiinfecciosos/química , Lípidos/química , Nanopartículas/química , Polímeros/química , Polimetil Metacrilato/química , Compuestos de Amonio Cuaternario/química , Tensoactivos/química , Antibacterianos/farmacología , Pruebas de Sensibilidad Microbiana , Staphylococcus aureus/efectos de los fármacosRESUMEN
Hybrid nanoparticles of poly(methylmethacrylate) synthesized in the presence of poly (diallyldimethyl ammonium) chloride by emulsion polymerization exhibited good colloidal stability, physical properties, and antimicrobial activity but their synthesis yielded poor conversion. Here we create antimicrobial coatings from casting and drying of the nanoparticles dispersions onto model surfaces such as those of silicon wafers, glass coverslips, or polystyrene sheets and optimize conversion using additional stabilizers such as cetyltrimethyl ammonium bromide, dioctadecyldimethyl ammonium bromide, or soybean lecithin during nanoparticles synthesis. Methodology included dynamic light scattering, determination of wettability, ellipsometry of spin-coated films, scanning electron microscopy, and determination of colony forming unities (log CFU/mL) of bacteria after 1 h interaction with the coatings. The additional lipids and surfactants indeed improved nanoparticle synthesis, substantially increasing the conversion rates by stabilizing the monomer droplets in dispersion during the polymerization. The coatings obtained by spin-coating or casting of the nanoparticles dispersions onto silicon wafers were hydrophilic with contact angles increasing with the amount of the cationic polymer in the nanoparticles. Against Escherichia coli and Staphylococcus aureus, bacteria cell counts were reduced by approximately 7 logs upon interaction with the coatings, revealing their potential for several biotechnological and biomedical applications.
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Antibacterianos/farmacología , Materiales Biocompatibles Revestidos/farmacología , Nanopartículas/química , Polímeros/farmacología , Coloides , Escherichia coli/efectos de los fármacos , Pruebas de Sensibilidad Microbiana , Nanopartículas/ultraestructura , Polietilenos/farmacología , Polimetil Metacrilato/farmacología , Compuestos de Amonio Cuaternario/farmacología , Solventes , Staphylococcus aureus/efectos de los fármacos , Tensoactivos/farmacologíaRESUMEN
Promiscuous inhibition due to aggregate formation has been recognized as a major concern in drug discovery campaigns. Here, we report some aggregators identified in a virtual screening (VS) protocol to search for inhibitors of human ecto-5'-nucleotidase (ecto-5'-NT/CD73), a promising target for several diseases and pathophysiological events, including cancer, inflammation and autoimmune diseases. Four compounds (A, B, C and D), selected from the ZINC-11 database, showed IC50 values in the micromolar range, being at the same time computationally predicted as potential aggregators. To confirm if they inhibit human ecto-5'-NT via promiscuous mechanism, forming aggregates, enzymatic assays were done in the presence of 0.01% (v/v) Triton X-100 and an increase in the enzyme concentration by 10-fold. Under both experimental conditions, these four compounds showed a significant decrease in their inhibitory activities. To corroborate these findings, turbidimetric assays were performed, confirming that they form aggregate species. Additionally, aggregation kinetic studies were done by dynamic light scattering (DLS) for compound C. None of the identified aggregators has been previously reported in the literature. For the first time, aggregation and promiscuous inhibition issues were systematically studied and evaluated for compounds selected by VS as potential inhibitors for human ecto-5'-NT. Together, our results reinforce the importance of accounting for potential false-positive hits acting by aggregation in drug discovery campaigns to avoid misleading assay results.
Asunto(s)
Inhibidores Enzimáticos/farmacología , Agregado de Proteínas/efectos de los fármacos , 5'-Nucleotidasa/química , Simulación por Computador , Bases de Datos de Compuestos Químicos , Evaluación Preclínica de Medicamentos , Dispersión Dinámica de Luz , Inhibidores Enzimáticos/química , Reacciones Falso Positivas , Proteínas Ligadas a GPI/química , Humanos , Concentración 50 Inhibidora , Nefelometría y TurbidimetríaRESUMEN
BACKGROUND: Several cationic polymers exhibit a useful antimicrobial property, however the structure-activity relationship still requires a more complete investigation. The main objective of this work is the comparison between the antimicrobial activity and toxicity of free and immobilized poly (diallyldimethylammonium) chloride (PDDA) in biocompatible poly (methylmethacrylate) (PMMA) nanoparticles (NPs). RESULTS: NPs synthesis by emulsion polymerization is performed over a range of [PDDA] at two methylmethacrylate (MMA) concentrations. The PMMA/PDDA dispersions are characterized by dynamic light-scattering for sizing, polydispersity and zeta-potential analysis, scanning electron microscopy (SEM), plating plus colony forming unities (CFU) counting for determination of the minimal microbicidal concentrations (MMC) against Escherichia coli, Staphylococcus aureus and Candida albicans and hemolysis evaluation against mammalian erythrocytes. There is a high colloidal stability for the cationic PMMA/PDDA NPs over a range of [PDDA]. NPs diverse antimicrobial activity against the microorganisms reduces cell viability by eight-logs (E. coli), seven-logs (S. aureus) or two-logs (C. albicans). The NPs completely kill E. coli over a range of [PDDA] that are innocuous to the erythrocytes. Free PDDA antimicrobial activity is higher than the one observed for PDDA in the NPs. There is no PDDA induced-hemolysis at the MMC in contrast to the hemolytic effect of immobilized PDDA in the NPs. Hemolysis is higher than 15 % for immobilized PDDA at the MMC for S. aureus and C. albicans. CONCLUSIONS: The mobility of the cationic antimicrobial polymer PDDA determines its access to the inner layers of the cell wall and the cell membrane, the major sites of PDDA antimicrobial action. PDDA freedom does matter for determining the antimicrobial activity at low PDDA concentrations and absence of hemolysis.
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Compuestos Alílicos/administración & dosificación , Compuestos Alílicos/farmacología , Antiinfecciosos/administración & dosificación , Antiinfecciosos/farmacología , Portadores de Fármacos/química , Nanopartículas/química , Polimetil Metacrilato/química , Compuestos de Amonio Cuaternario/administración & dosificación , Compuestos de Amonio Cuaternario/farmacología , Compuestos Alílicos/química , Antiinfecciosos/química , Candida albicans/efectos de los fármacos , Candidiasis/tratamiento farmacológico , Escherichia coli/efectos de los fármacos , Infecciones por Escherichia coli/tratamiento farmacológico , Humanos , Pruebas de Sensibilidad Microbiana , Nanopartículas/ultraestructura , Compuestos de Amonio Cuaternario/química , Infecciones Estafilocócicas/tratamiento farmacológico , Staphylococcus aureus/efectos de los fármacosRESUMEN
The genus Panochthus represents the last lineage of "Panochthini" recorded in the Pleistocene. This genus has a wide latitudinal distribution in South America, and in Brazil it occurs in the southern and northeastern regions. In this paper we describe new material (isolated osteoderms and caudal tube fragments) assigned to Panochthus from the state of Rio Grande do Sul (southern Brazil) and discuss some taxonomic issues related to Panochthus tuberculatus and Panochthus greslebini based on this material . The occurrence of P. greslebini is the first for outside the Brazilian Intertropical Region. In addition, we describe new diagnostic features to differentiate the osteoderms of P. greslebini and P. tuberculatus. Unfortunately, it was not possible to identify some osteoderms at the species level. Interestingly, they showed four distinct morphotypes characterized by their external morphology, and thus were attributed to Panochthus sp. Lastly, we conclude that in addition to P.tuberculatus registered to southern Brazil, there is another species of the genus, assignable to P. cf. P. greslebini. Our analysis reinforce the reliability of caudal tube characters for the classification of species of Panochthus.
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Fósiles , Xenarthra/clasificación , Animales , Brasil , Paleontología , Xenarthra/anatomía & histologíaRESUMEN
The growing challenge of antimicrobial resistance to antibiotics requires novel synthetic drugs or new formulations for old drugs. Here, cationic nanostructured particles (NPs) self-assembled from cationic bilayer fragments and polyelectrolytes are tested against four multidrug-resistant (MDR) strains of clinical importance. The non-hemolytic poly(diallyldimethylammonium) chloride (PDDA) polymer as the outer NP layer shows a remarkable activity against these organisms. The mechanism of cell death involves bacterial membrane lysis as determined from the leakage of inner phosphorylated compounds and possibly disassembly of the NP with the appearance of multilayered fibers made of the NP components and the biopolymers withdrawn from the cell wall. The NPs display broad-spectrum activity against MDR microorganisms, including Gram-negative and Gram-positive bacteria and yeast.
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Antibacterianos/farmacología , Farmacorresistencia Bacteriana Múltiple , Bacterias Gramnegativas/efectos de los fármacos , Bacterias Grampositivas/efectos de los fármacos , Pruebas de Sensibilidad Microbiana , Polietilenos/farmacología , Compuestos de Amonio Cuaternario/farmacologíaRESUMEN
The Brazilian records on Xenacanthiformes include teeth and cephalic spines from the Parnaíba, Amazonas and Paraná basins. This work describes a new species of Xenacanthidae, collected in an outcrop of Serrinha Member of Rio do Rasto Formation (Wordian to Wuchiapingian), Paraná Basin, municipality of Jacarezinho, State of Paraná. The teeth of the new species are two or three-cuspidated and the aboral surface show a smooth concavity and one rounded basal tubercle. The coronal surface presents one semi-spherical and subcircular coronal button, and also two lateral main cusps and one central (when present) with less than one fifth of the size of the lateral cusps in the labial portion. The lateral cusps are asymmetric or symmetric, rounded in transversal section, lanceolate in longitudinal section, devoid of lateral carinae and lateral serrations, and with few smooth cristae of enameloid. In optical microscope the teeth show a trabecular dentine (osteodentine) base, while the cusps are composed by orthodentine, and the pulp cavities are non-obliterated by trabecular dentine. The fossil assemblage in the same stratigraphical level and in the whole Rio do Rasto Formation indicates another freshwater record for xenacanthid sharks.
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Fósiles , Sedimentos Geológicos , Tiburones/clasificación , Animales , Brasil , PaleontologíaRESUMEN
This paper deals with xenarthrans osteoderms assigned to Dasypus aff. D. novemcinctus, Euphractus sexcinctus and Cabassous sp. The material was collected in subsurface, from 0.10 to 0.60 m in the Urso Fóssil Cave, Parque Nacional de Ubajara, State of Ceará, northeastern Brazil. The ages of sediment samples from levels 4 and 5 (depths of 0.40 and 0.50 m) were determined by thermoluminescence technique, and indicated ages of 8,000 and 8,200 years BP for each layer respectively. The presence in these layers of early Holocene xenarthrans taxa can contribute to the understanding of the biotic evolution of the northwest region of Ceará during the last 10,000 years. Two of the three identified taxa still occur in the region: Dasypus novemcinctus and Euphractus sexcinctus. The Dasypodidae fauna here reported includes animals with generalist feeding habits and current wide geographical distribution. It is suggested, therefore, that the climatic and environmental conditions in the early Holocene were very similar the actual ones, and that the absence of Cabassous may be conditioned to other factors, such as anthropogenic action and loss of habitat by fragmentation of the vegetation.
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Fósiles , Xenarthra/clasificación , Animales , Brasil , PaleontologíaRESUMEN
The coastal plain of the state of Rio Grande do Sul, in southern Brazil, includes four barrier-lagoon depositional systems formed by successive Quaternary sea-level highstands that were correlated to marine isotope stages (MIS) 11, 9, 5 and 1, despite the scarcity of absolute ages. This study describes a sea-level highstand older than MIS 5, based on the stratigraphy, ages and fossils of the shallow marine facies found in coastal barrier (Barrier II). This facies outcrops along the banks of Chuí Creek, it is composed of fine, well-sorted quartz sand and contains ichnofossils Ophiomorpha nodosa and Rosselia sp., and molluscan shells. The sedimentary record indicates coastal aggradation followed by sea-level fall and progradation of the coastline. Thermoluminescence (TL) and electron spin resonance (ESR) ages from sediments and fossil shells point to an age of â¼220 ka for the end of this marine transgression, thus correlating it to MIS 7 (substage 7e). Altimetric data point to a maximum amplitude of about 10 meters above present-day mean sea-level, but tectonic processes may be involved. Paleoceanographic conditions at the time of the highstand and correlations with other deposits in the Brazilian coasts are also discussed.
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Organismos Acuáticos , Fósiles , Agua de Mar , Animales , Brasil , Sedimentos Geológicos , Paleontología , Radioisótopos/análisis , Datación RadiométricaRESUMEN
Peptides in general hold much promise as a major ingredient in novel supramolecular assemblies. They may become essential in vaccine design, antimicrobial chemotherapy, cancer immunotherapy, food preservation, organs transplants, design of novel materials for dentistry, formulations against diabetes and other important strategical applications. This review discusses how novel formulations may improve the therapeutic index of antimicrobial peptides by protecting their activity and improving their bioavailability. The diversity of novel formulations using lipids, liposomes, nanoparticles, polymers, micelles, etc., within the limits of nanotechnology may also provide novel applications going beyond antimicrobial chemotherapy.
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Antiinfecciosos/química , Péptidos Catiónicos Antimicrobianos/química , Antiinfecciosos/metabolismo , Antiinfecciosos/farmacología , Péptidos Catiónicos Antimicrobianos/metabolismo , Péptidos Catiónicos Antimicrobianos/farmacología , Bacterias/efectos de los fármacos , Materiales Biocompatibles/química , Química Farmacéutica , Ciclosporina/química , Ciclosporina/metabolismo , Portadores de Fármacos/química , Humanos , Membrana Dobles de Lípidos/química , Membrana Dobles de Lípidos/metabolismoRESUMEN
Among the living tetrapods, mammals present a unique tooth replacement pattern, diphyodonty. Therefore, studying the dentition of mammalian ancestors is relevant to a better understanding of how this remarkable feature evolved. However, little is known about the postcanine tooth replacement pattern among Triassic cynodonts. Here, we applied the nondestructive method of microcomputed tomography (microCT) to analyze the dentition of the enigmatic Upper Triassic sectorial-toothed cynodont Charruodon tetracuspidatus (MCP 3934 PV, holotype) from the Candelaria Sequence, Santa Maria Supersequence, Brazil. The microCT-scan data allowed visualization of the replacement dentition and roots of the functional teeth, which provided information to inform interpretations of the ontogenetic stage and taxonomy of the species. A combination of dental and mandibular traits, as well as the small size of the specimen MCP 3934 PV, suggest an early ontogenetic stage. Additionally, the specimen could potentially be an ontogenetically immature form of another taxon, or a yet unknown species of probainognathian cynodont. Therefore, Charruodon tetracuspidatus is here designated as a nomen dubium, given the challenges of maintaining the species as valid.
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Dentición , Diente , Animales , Filogenia , Microtomografía por Rayos X , Brasil , Fósiles , Diente/diagnóstico por imagen , MamíferosRESUMEN
Investigating the evolutionary trajectory of synapsid sensory and cephalic systems is pivotal for understanding the emergence and diversification of mammals. Recent studies using CT-scanning to analyze the rostral foramina and maxillary canals morphology in fossilized specimens of probainognathian cynodonts have contributed to clarifying the homology and paleobiological interpretations of these structures. In the present work, µCT-scannings of three specimens of Riograndia guaibensis, an early Norian cynodont from southern Brazil, were analyzed and revealed an incomplete separation between the lacrimal and maxillary canals, with points of contact via non-ossified areas. While the maxillary canal exhibits a consistent morphological pattern with other Prozostrodontia, featuring three main branches along the lateral region of the snout, the rostral alveolar canal in Riograndia displays variability in the number of extra branches terminating in foramina on the lateral surface of the maxilla, showing differences among individuals and within the same skull. Additionally, pneumatization is observed in the anterior region of the skull, resembling similar structures found in reptiles and mammals. Through this pneumatization, certain branches originating from the maxillary canal extend to the canine alveolus. Further investigation is warranted to elucidate the functionality of this structure and its occurrence in other cynodont groups.
RESUMEN
Decuriasuchus quartacolonia is a middle-sized basal "rauisuchian" (Pseudosuchia, Loricata) from the Triassic beds of Brazil, whose original description was based on 10 specimens of equivalent size found in aggregation. In this contribution, we explore the osteohistology of its appendicular bones and a rib, aiming to infer growth patterns and ontogeny. In all analyzed bones (except in the rib) from three individuals, we found fibrolamellar bone (FLB) throughout the cortices, a pattern shared with other histologically sampled basal loricatans. We found evidence that suggests an early ontogenetic stage for all studied specimens: absence of secondary osteons, lack of transition from an inner highly vascularized FLB matrix to a poor vascularized parallel-fibred bone, one line of arrested growth, open vascular canals in the external surface of the cortex and absence of an external fundamental system. In addition, we observed that the neurocentral sutures in the caudal to cervical vertebrae of the holotype are unfused, strongly suggesting that these individuals were not skeletally mature, as had been previously assumed. In addition, our data support the prior hypothesis that Decuriasuchus is the oldest-known archosaur to show evidence of gregarious behavior and adds a probable cause of this as a strategy to obtain food and avoid predation until becoming independent as adults. Furthermore, our results open the possibility that Decuriasuchus may represent an earlier growth stage of the larger Prestosuchus chiniquensis, with two specimens recovered from the same stratigraphic level and paleontological site. Since the adult form of Decuriasuchus remains unknown, a deeper anatomical study is needed to discuss the validity of the species. This study case exemplifies the importance of paleohistology as an essential complementary tool to describe a new morphospecies in vertebrate paleontology.
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Fósiles , Paleontología , Humanos , Animales , Brasil , Huesos , VertebradosRESUMEN
The nasal cavity of living mammals is a unique structural complex among tetrapods, acquired along a series of major morphological transformations that occurred mainly during the Mesozoic Era, within the Synapsida clade. Particularly, non-mammaliaform cynodonts document several morphological changes in the skull, during the Triassic Period, that represent the first steps of the mammalian bauplan. We here explore the nasal cavity of five cynodont taxa, namely Thrinaxodon, Chiniquodon, Prozostrodon, Riograndia, and Brasilodon, in order to discuss the main changes within this skull region. We did not identify ossified turbinals in the nasal cavity of these taxa and if present, as non-ossified structures, they would not necessarily be associated with temperature control or the development of endothermy. We do, however, notice a complexification of the cartilage anchoring structures that divide the nasal cavity and separate it from the brain region in these forerunners of mammals.
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Fósiles , Mamíferos , Cráneo , Cornetes Nasales , Microtomografía por Rayos X , Animales , Mamíferos/anatomía & histología , Fósiles/anatomía & histología , Cráneo/anatomía & histología , Cráneo/diagnóstico por imagen , América del Sur , Cornetes Nasales/anatomía & histología , Cornetes Nasales/diagnóstico por imagen , Evolución Biológica , Cavidad Nasal/anatomía & histología , Cavidad Nasal/diagnóstico por imagen , FilogeniaRESUMEN
The present study investigated the effects of ΔΨ and ΔpH (pH gradient) on the interaction of cytochrome c with a mitochondrial mimetic membrane composed of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and cardiolipin (CL) leading to vesicle fusion. ΔpH generated by lowered bulk pH (pH(out)) of PCPECL liposomes, with an internal pH (pH(in)) of 8.0, favored vesicle fusion with a titration sigmoidal profile (pK(a) ~ 6.9). Conversely, ΔpH generated by enhanced pH(in) of PCPECL at a pH(out) of 6.0 favored the fusion of vesicles with a linear profile. We did not observe a significant amount of liposome fusion when ΔpH was generated by lowered pH(in) at a pH(out) of 8.0. At bulk acidic pH, ΔΨ generated by Na⺠gradient also favored cyt c-promoted vesicle fusion. At acidic and alkaline pH(out), the presence of ΔpH and ΔΨ did not affect cytochrome c binding affinity measured by pyrene quenching. Therefore, cytochrome c-mediated PC/PE/CL vesicle fusion is dependent of ionization of the protein site L (acidic pH) and the presence of transmembrane potential. The effect of transmembrane potential is probably related to the generation of defects on the lipid bilayer. These results are consistent with previous reports showing that cytochrome c release prior to the dissipation of the ΔΨ(M) blocks inner mitochondrial membrane fusion during apoptosis.
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Citocromos c/química , Citocromos c/metabolismo , Membranas Mitocondriales/química , Membranas Mitocondriales/metabolismo , Animales , Caballos , Humanos , Concentración de Iones de Hidrógeno , Fusión de Membrana , Potenciales de la Membrana/fisiologíaRESUMEN
Cationic compounds are promising candidates for development of antimicrobial agents. Positive charges attached to surfaces, particles, polymers, peptides or bilayers have been used as antimicrobial agents by themselves or in sophisticated formulations. The main positively charged moieties in these natural or synthetic structures are quaternary ammonium groups, resulting in quaternary ammonium compounds (QACs). The advantage of amphiphilic cationic polymers when compared to small amphiphilic molecules is their enhanced microbicidal activity. Besides, many of these polymeric structures also show low toxicity to human cells; a major requirement for biomedical applications. Determination of the specific elements in polymers, which affect their antimicrobial activity, has been previously difficult due to broad molecular weight distributions and random sequences characteristic of radical polymerization. With the advances in polymerization control, selection of well defined polymers and structures are allowing greater insight into their structure-antimicrobial activity relationship. On the other hand, antimicrobial polymers grafted or self-assembled to inert or non inert vehicles can yield hybrid antimicrobial nanostructures or films, which can act as antimicrobials by themselves or deliver bioactive molecules for a variety of applications, such as wound dressing, photodynamic antimicrobial therapy, food packing and preservation and antifouling applications.