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BACKGROUND: Patients with brain injury who are unresponsive to commands may perform cognitive tasks that are detected on functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). This phenomenon, known as cognitive motor dissociation, has not been systematically studied in a large cohort of persons with disorders of consciousness. METHODS: In this prospective cohort study conducted at six international centers, we collected clinical, behavioral, and task-based fMRI and EEG data from a convenience sample of 353 adults with disorders of consciousness. We assessed the response to commands on task-based fMRI or EEG in participants without an observable response to verbal commands (i.e., those with a behavioral diagnosis of coma, vegetative state, or minimally conscious state-minus) and in participants with an observable response to verbal commands. The presence or absence of an observable response to commands was assessed with the use of the Coma Recovery Scale-Revised (CRS-R). RESULTS: Data from fMRI only or EEG only were available for 65% of the participants, and data from both fMRI and EEG were available for 35%. The median age of the participants was 37.9 years, the median time between brain injury and assessment with the CRS-R was 7.9 months (25% of the participants were assessed with the CRS-R within 28 days after injury), and brain trauma was an etiologic factor in 50%. We detected cognitive motor dissociation in 60 of the 241 participants (25%) without an observable response to commands, of whom 11 had been assessed with the use of fMRI only, 13 with the use of EEG only, and 36 with the use of both techniques. Cognitive motor dissociation was associated with younger age, longer time since injury, and brain trauma as an etiologic factor. In contrast, responses on task-based fMRI or EEG occurred in 43 of 112 participants (38%) with an observable response to verbal commands. CONCLUSIONS: Approximately one in four participants without an observable response to commands performed a cognitive task on fMRI or EEG as compared with one in three participants with an observable response to commands. (Funded by the James S. McDonnell Foundation and others.).
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Transtornos da Consciência , Eletroencefalografia , Imageamento por Ressonância Magnética , Humanos , Feminino , Masculino , Adulto , Estudos Prospectivos , Pessoa de Meia-Idade , Transtornos da Consciência/etiologia , Transtornos da Consciência/fisiopatologia , Cognição/fisiologia , Encéfalo/diagnóstico por imagem , Encéfalo/fisiopatologia , Lesões Encefálicas/fisiopatologia , Lesões Encefálicas/complicações , Lesões Encefálicas/diagnóstico por imagem , Idoso , Adulto Jovem , Estado Vegetativo Persistente/fisiopatologia , Estado Vegetativo Persistente/etiologiaRESUMO
Inflammatory conditions, including allergic asthma and conditions in which chronic low-grade inflammation is a risk factor, such as stress-related psychiatric disorders, are prevalent and are a significant cause of disability worldwide. Novel approaches for the prevention and treatment of these disorders are needed. One approach is the use of immunoregulatory microorganisms, such as Mycobacterium vaccae NCTC 11659, which have anti-inflammatory, immunoregulatory, and stress-resilience properties. However, little is known about how M. vaccae NCTC 11659 affects specific immune cell targets, including monocytes, which can traffic to peripheral organs and the central nervous system and differentiate into monocyte-derived macrophages that, in turn, can drive inflammation and neuroinflammation. In this study, we investigated the effects of M. vaccae NCTC 11659 and subsequent lipopolysaccharide (LPS) challenge on gene expression in human monocyte-derived macrophages. THP-1 monocytes were differentiated into macrophages, exposed to M. vaccae NCTC 11659 (0, 10, 30, 100, 300 µg/mL), then, 24 h later, challenged with LPS (0, 0.5, 2.5, 250 ng/mL), and assessed for gene expression 24 h following challenge with LPS. Exposure to M. vaccae NCTC 11659 prior to challenge with higher concentrations of LPS (250 ng/mL) polarized human monocyte-derived macrophages with decreased IL12A, IL12B, and IL23A expression relative to IL10 and TGFB1 mRNA expression. These data identify human monocyte-derived macrophages as a direct target of M. vaccae NCTC 11659 and support the development of M. vaccae NCTC 11659 as a potential intervention to prevent stress-induced inflammation and neuroinflammation implicated in the etiology and pathophysiology of inflammatory conditions and stress-related psychiatric disorders.
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Lipopolissacarídeos , Mycobacterium , Humanos , Lipopolissacarídeos/farmacologia , Doenças Neuroinflamatórias , Inflamação , MacrófagosRESUMO
PREMISE: Lichen-forming fungi that colonize leaf surfaces must find a compatible algal symbiont, establish lichen symbiosis, and reproduce within the limited life span of their substratum. Many produce specialized asexual propagules that appear to be dispersed by rain and runoff currents, but less is known about dispersal of their meiotic ascospores. In some taxa, a layer of algal symbionts covers the hymenial surface of the apothecia, where asci discharge their ascospores. We examined the untested hypothesis that their ascospores are ejected into air currents and carry with them algal symbionts from the epihymenial layer for subsequent lichenization. METHODS: Leaves bearing the lichens Calopadia puiggarii, Sporopodium marginatum (Pilocarpaceae), and Gyalectidium viride (Gomphillaceae) were collected in southern Florida. The latter two species have epihymenial algal layers. Leaf fragments with apotheciate thalli were affixed in petri dishes, with glass cover slips attached inside the lid over the thalli. Subsequent discharge of ascospores and any co-dispersed algae was evaluated with light microscopy. RESULTS: All three species discharged ascospores aerially. Discharged ascospores were frequently surrounded by a halo-like sheath of transparent material. In the two species with an epihymenial algal layer, most dispersing ascospores (>90%) co-transported algal cells attached to the spore sheath or wall. CONCLUSIONS: While water may be the usual vector for their asexual propagules, foliicolous lichen-forming fungi make use of air currents to disperse their ascospores. The epihymenial algal layer represents an adaptation for efficient co-dispersal of the algal symbiont with the next genetic generation of the fungus.
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Líquens , Florida , Líquens/microbiologia , Folhas de Planta , SimbioseRESUMO
The recently described genus Rhizonema is among the most important cyanobacterial partners in lichen symbioses, but its morphological characterization in the genus diagnosis-true branching of the T-type-appears at odds with several published figures showing false branching. We investigated cyanobiont branching and cell division with light microscopy in two basidiolichens from Florida and one from Japan, including aposymbiotically cultured material of the latter. Mycobiont species identities (Cyphellostereum jamesianum, Dictyonema darwinianum, and D. moorei) and photobiont genus identity (Rhizonema) were corroborated with ITS and rbcLX sequences, respectively. Single and paired false branching occurred commonly in all three strains examined. False branches developed adjacent to necridic cells or heterocytes, or by separation of vegetative cells at compression folds in the trichome. Non-transverse cell divisions, usually oblique, were observed in two of the three Rhizonema strains examined. T-type true branches sometimes arose from such divisions, although oblique growth from the branch cell often resulted in ambiguous branch junctions. Additionally, Y-type true branches appeared to grow from contorted filaments. In cultured material, a kind of pseudo-branch sometimes arose from single- or several-celled segments liberated from trichome apices. The segments attached secondarily to filaments and grew there as apparent branches. We conclude that Rhizonema is a genus of considerable morphological flexibility, with multiple modes of branching possible in a single strain. While true branching or non-transverse divisions, when observable, may help distinguish Rhizonema from the phenotypically similar Scytonema, false branching occurs commonly in both genera, and therefore cannot be used to distinguish them.
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Cianobactérias , Líquens , Florida , Filogenia , SimbioseRESUMO
OBJECTIVE: The USA needs to produce more psychiatrists to meet projected workforce deficits. The American Association of Directors of Psychiatric Residency Training Directors (AADPRT) sought to examine opportunities for and obstacles to expanding or creating residencies and fellowships. METHODS: In November 2019, the authors conducted a survey of residency and fellowship directors. The survey gathered information about new positions, new programs, participation in interprofessional education, and loss of residency or fellowship positions. RESULTS: The survey was distributed to psychiatry residency (N=231) and fellowship (N=194) directors, with a response rate of 33.4%. One quarter of responding residencies and fellowships reported creating new programs; 24.7% of residency and 17.5% of fellowships reported expansion. The most common reason to develop or expand programs was the shortage of psychiatrists, with the local institution as the most common funding source. Fifty-seven percent reported that they had wanted to expand, but faced barriers, primarily lack of funding. Recruitment and retention of faculty are major challenges. Psychiatry departments frequently (87.5%) participate in interprofessional education, generally perceived as positive. Unfortunately, 15.7% of respondents reported loss of positions or closure of programs. CONCLUSIONS: Creating and expanding residencies and fellowships are common strategies for addressing the shortage of psychiatrists. Barriers include lack of funding and challenges recruiting/retaining faculty. The loss of residency/fellowship positions or closure of programs is a worrisome trend.
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Internato e Residência , Psiquiatria , Educação de Pós-Graduação em Medicina , Bolsas de Estudo , Humanos , Inquéritos e Questionários , Estados Unidos , Recursos HumanosRESUMO
PURPOSE OF REVIEW: Refinement in machine learning (ML) techniques and approaches has rapidly expanded artificial intelligence applications for the diagnosis and classification of heart failure (HF). This review is designed to provide the clinician with the basics of ML, as well as this technologies future utility in HF diagnosis and the potential impact on patient outcomes. RECENT FINDINGS: Recent studies applying ML methods to unique data sets available from electrocardiography, vectorcardiography, echocardiography, and electronic health records show significant promise for improving diagnosis, enhancing detection, and advancing treatment of HF. Innovations in both supervised and unsupervised methods have heightened the diagnostic accuracy of models developed to identify the presence of HF and further augmentation of model capabilities are likely utilizing ensembles of ML algorithms derived from different techniques. SUMMARY: This article is an overview of recent applications of ML to achieve improved diagnosis of HF and the resultant implications for patient management.
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Inteligência Artificial , Insuficiência Cardíaca , Algoritmos , Eletrocardiografia , Insuficiência Cardíaca/diagnóstico , Humanos , Aprendizado de MáquinaRESUMO
We report counter-intuitive axial preferences in non-stereochemically biased, selectively fluorinated methoxycyclohexanes. These pseudo-anomeric effects are apparent when electronegative CF2 groups are placed at the C-2, C-4 and C-6 positions of the cyclohexane ring to render the C-3/5 axial hydrogen atoms electropositive. The electrostatic interaction between these axial hydrogen atoms and the -OMe oxygen is stabilising. The effect is explored using high-level ab initio and DFT calculations in the framework of NBO, QTAIM and NCI analysis across a range of derivatives, and experimentally (19 F{1 H}-NMR at -80 °C) for some illustrative examples. The effect is significant in energy terms for a weak interaction, and illustrates a new stereoelectronic aspect attributed to selective fluorine substitution in organic chemistry.
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The early Pliocene site of Kanapoi (Turkana Basin, Kenya) has a large, diverse vertebrate sample that contains the earliest representatives of the hominin genus Australopithecus. Included in this sample is an impressive assemblage of fossil proboscideans, comprised of deinotheres (Deinotherium bozasi), anancine gomphotheres (Anancus ultimus), and at least three species of elephant (Loxodonta adaurora, a primitive morph of Loxodonta exoptata, and Elephas ekorensis). A single specimen from high in the sequence could plausibly belong to a primitive stage of Elephas recki. A review of dental carbon isotope analyses indicates a range of dietary habits for these taxa, from dedicated browsing (deinotheres) to mixed feeding/grazing (elephants and gomphotheres), which in early Pliocene elephants corresponds to molars with greater crown height and more plates than in late Miocene confamilials, bringing their morphology more in phase with feeding behavior than was the case in their earlier relatives. Variation in feeding preferences among Kanapoi proboscideans corresponds to evidence for habitat heterogeny, including inferred substantial presence of grasses; the occurrence of multiple megaherbivores may have contributed to the fragmentation of ecosystems, positively affecting early hominin success and aiding diversification of other ungulate groups.
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Evolução Biológica , Biota , Dieta/veterinária , Comportamento Alimentar , Fósseis/anatomia & histologia , Mamífero Proboscídeo/classificação , Animais , Meio Ambiente , Quênia , Mamífero Proboscídeo/anatomia & histologia , DenteRESUMO
Reactive oxygen species (ROS) are formed in mitochondria during electron transport and energy generation. Elevated levels of ROS lead to increased amounts of mitochondrial DNA (mtDNA) damage. We report that levels of M1dG, a major endogenous peroxidation-derived DNA adduct, are 50-100-fold higher in mtDNA than in nuclear DNA in several different human cell lines. Treatment of cells with agents that either increase or decrease mitochondrial superoxide levels leads to increased or decreased levels of M1dG in mtDNA, respectively. Sequence analysis of adducted mtDNA suggests that M1dG residues are randomly distributed throughout the mitochondrial genome. Basal levels of M1dG in mtDNA from pulmonary microvascular endothelial cells (PMVECs) from transgenic bone morphogenetic protein receptor 2 mutant mice (BMPR2R899X) (four adducts per 106 dG) are twice as high as adduct levels in wild-type cells. A similar increase was observed in mtDNA from heterozygous null (BMPR2+/-) compared to wild-type PMVECs. Pulmonary arterial hypertension is observed in the presence of BMPR2 signaling disruptions, which are also associated with mitochondrial dysfunction and oxidant injury to endothelial tissue. Persistence of M1dG adducts in mtDNA could have implications for mutagenesis and mitochondrial gene expression, thereby contributing to the role of mitochondrial dysfunction in diseases.
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DNA Mitocondrial/metabolismo , Mitocôndrias/genética , Estresse Oxidativo/genética , Nucleosídeos de Purina/metabolismo , Animais , Receptores de Proteínas Morfogenéticas Ósseas Tipo II/genética , Adutos de DNA/genética , Adutos de DNA/metabolismo , DNA Mitocondrial/genética , Transporte de Elétrons/efeitos dos fármacos , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/metabolismo , Regulação da Expressão Gênica/genética , Humanos , Hipertensão Pulmonar/genética , Hipertensão Pulmonar/metabolismo , Hipertensão Pulmonar/patologia , Peroxidação de Lipídeos/genética , Camundongos , Camundongos Transgênicos , Mitocôndrias/patologia , Mutagênese/genética , Oxidantes/farmacologia , Nucleosídeos de Purina/biossíntese , Espécies Reativas de Oxigênio/química , Superóxidos/metabolismoRESUMO
The reniform nematode (Rotylenchulus reniformis) is a sedentary semi-endoparasitic species that is pathogenic on many row crops, fruits, and vegetables. Here, the authors present a draft genome assembly of R. reniformis using small- and large-insert libraries sequenced on the Illumina GAIIx and MiSeq platforms.The reniform nematode (Rotylenchulus reniformis) is a sedentary semi-endoparasitic species that is pathogenic on many row crops, fruits, and vegetables. Here, the authors present a draft genome assembly of R. reniformis using small- and large-insert libraries sequenced on the Illumina GAIIx and MiSeq platforms.
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Polyploidy often confers emergent properties, such as the higher fibre productivity and quality of tetraploid cottons than diploid cottons bred for the same environments. Here we show that an abrupt five- to sixfold ploidy increase approximately 60 million years (Myr) ago, and allopolyploidy reuniting divergent Gossypium genomes approximately 1-2 Myr ago, conferred about 30-36-fold duplication of ancestral angiosperm (flowering plant) genes in elite cottons (Gossypium hirsutum and Gossypium barbadense), genetic complexity equalled only by Brassica among sequenced angiosperms. Nascent fibre evolution, before allopolyploidy, is elucidated by comparison of spinnable-fibred Gossypium herbaceum A and non-spinnable Gossypium longicalyx F genomes to one another and the outgroup D genome of non-spinnable Gossypium raimondii. The sequence of a G. hirsutum A(t)D(t) (in which 't' indicates tetraploid) cultivar reveals many non-reciprocal DNA exchanges between subgenomes that may have contributed to phenotypic innovation and/or other emergent properties such as ecological adaptation by polyploids. Most DNA-level novelty in G. hirsutum recombines alleles from the D-genome progenitor native to its New World habitat and the Old World A-genome progenitor in which spinnable fibre evolved. Coordinated expression changes in proximal groups of functionally distinct genes, including a nuclear mitochondrial DNA block, may account for clusters of cotton-fibre quantitative trait loci affecting diverse traits. Opportunities abound for dissecting emergent properties of other polyploids, particularly angiosperms, by comparison to diploid progenitors and outgroups.
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Evolução Biológica , Fibra de Algodão , Genoma de Planta/genética , Gossypium/genética , Poliploidia , Alelos , Cacau/genética , Cromossomos de Plantas/genética , Diploide , Duplicação Gênica/genética , Genes de Plantas/genética , Gossypium/classificação , Anotação de Sequência Molecular , Filogenia , Vitis/genéticaRESUMO
The reniform nematode (Rotylenchulus reniformis Linford and Oliveira) is a semi-endoparasitic nematode that is a pathogen of numerous major crops such as cotton and soybean. Here, the authors present transcriptome assemblies of the egg, second-stage juvenile (J2), J3, vermiform adult, and sedentary female life stages of this important plant pathogen.The reniform nematode (Rotylenchulus reniformis Linford and Oliveira) is a semi-endoparasitic nematode that is a pathogen of numerous major crops such as cotton and soybean. Here, the authors present transcriptome assemblies of the egg, second-stage juvenile (J2), J3, vermiform adult, and sedentary female life stages of this important plant pathogen.
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BACKGROUND: Epidural glucocorticoid injections are widely used to treat symptoms of lumbar spinal stenosis, a common cause of pain and disability in older adults. However, rigorous data are lacking regarding the effectiveness and safety of these injections. METHODS: In a double-blind, multisite trial, we randomly assigned 400 patients who had lumbar central spinal stenosis and moderate-to-severe leg pain and disability to receive epidural injections of glucocorticoids plus lidocaine or lidocaine alone. The patients received one or two injections before the primary outcome evaluation, performed 6 weeks after randomization and the first injection. The primary outcomes were the score on the Roland-Morris Disability Questionnaire (RMDQ, in which scores range from 0 to 24, with higher scores indicating greater physical disability) and the rating of the intensity of leg pain (on a scale from 0 to 10, with 0 indicating no pain and 10 indicating "pain as bad as you can imagine"). RESULTS: At 6 weeks, there were no significant between-group differences in the RMDQ score (adjusted difference in the average treatment effect between the glucocorticoid-lidocaine group and the lidocaine-alone group, -1.0 points; 95% confidence interval [CI], -2.1 to 0.1; P=0.07) or the intensity of leg pain (adjusted difference in the average treatment effect, -0.2 points; 95% CI, -0.8 to 0.4; P=0.48). A prespecified secondary subgroup analysis with stratification according to type of injection (interlaminar vs. transforaminal) likewise showed no significant differences at 6 weeks. CONCLUSIONS: In the treatment of lumbar spinal stenosis, epidural injection of glucocorticoids plus lidocaine offered minimal or no short-term benefit as compared with epidural injection of lidocaine alone. (Funded by the Agency for Healthcare Research and Quality; ClinicalTrials.gov number, NCT01238536.).
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Anestésicos Locais/uso terapêutico , Glucocorticoides/uso terapêutico , Lidocaína/uso terapêutico , Estenose Espinal/tratamento farmacológico , Idoso , Anestésicos Locais/efeitos adversos , Método Duplo-Cego , Quimioterapia Combinada , Feminino , Glucocorticoides/efeitos adversos , Humanos , Hidrocortisona/sangue , Injeções Epidurais , Lidocaína/efeitos adversos , Vértebras Lombares , Masculino , Pessoa de Meia-Idade , Dor/tratamento farmacológico , Dor/etiologia , Medição da Dor , Estenose Espinal/complicações , Resultado do TratamentoAssuntos
Transferência Genética Horizontal , Plantas , Evolução Biológica , Fotossíntese , Filogenia , Plastídeos , SimbioseRESUMO
PREMISE OF THE STUDY: Lichen-forming fungi produce diverse vegetative tissues, some closely resembling those of plants. Yet it has been repeatedly affirmed that none is a true parenchyma, in which cellular compartments are subdivided from all adjacent neighbors by cross walls adjoining older cross walls. METHODS: Using transmission electron microscopy (TEM), we tested this assumption by examining patterns of septum formation in the parenchyma-like cortex of three lichens of different phylogenetic affinities: Sticta canariensis, Leptogium cyanescens, and Endocarpon pusillum. KEY RESULTS: In the cortex of all three lichens, new septa adjoined perpendicularly or obliquely to previous septa. Septal walls possessed an electron-transparent core (median) layer covered on both sides by layers of intermediate electron density. At septal junctures, the core layer of the newer septum was not continuous with that of the older septum. Amorphous, electron-dense material often became deposited in the core region of older septal walls, and the septum gradually delaminated along its median into what could then be recognized as the distinct walls of neighboring cells. However, cells maintained continuity at pores, where adjacent remnants of the electron-transparent core layer suggested septal partition rather than secondary establishment of a lateral wall connection via anastomosis. CONCLUSIONS: Although fungal tissues first arise by the coalescence of filaments early in lichen ontogeny, the mature cortical tissues of some lichens are comparable to true parenchyma in the unrestricted orientation of their septal cross walls and the resulting ontogenetic relationship among neighboring cell compartments.
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Ascomicetos/fisiologia , Líquens/microbiologia , Simbiose/fisiologia , Ascomicetos/citologia , Ascomicetos/ultraestrutura , Parede Celular/fisiologia , Parede Celular/ultraestrutura , Líquens/citologia , Líquens/ultraestrutura , Microscopia Eletrônica de Transmissão , Especificidade da EspécieRESUMO
PREMISE OF THE STUDY: Some common leaf-dwelling lichen fungi produce asexual spores (conidia) within curved, dorsiventral structures called campylidia. Their shape and tendency to face in the same direction have generated speculation about how dispersal is accomplished. Here we tested the hypothesis that campylidia orient their spore-producing surface against runoff currents and examined the effects of hydration to better understand the spore dispersal mechanism. METHODS: Palm leaves bearing lichens (Calopadia) were surveyed with a dissecting microscope for campylidia with fibrous debris entangled around the base. Where possible, the direction of runoff flow was inferred from the position of the entangled debris; the angle between this direction and that toward which the spore-producing side faced was calculated for 67 campylidia. Other fresh-collected campylidia were photographed in the air-dry state and again after hydration. KEY RESULTS: Orientation of campylidia was strongly correlated with direction of runoff flow, such that the spore-producing side faced against oncoming runoff. Hydration of campylidia quickly resulted in swelling of the conidial mass beneath a thin flap of tissue covering the conidiogenous surface. The flap then bulged outward, exposing the conidial mass from above within its pocket-like compartment. CONCLUSIONS: Our results support previous contentions that water impact against campylidia is important in spore dispersal. However, the morphology of hydrated campylidia and their strong tendency to face upstream suggest that water currents impact laterally upon the thin tissue covering the hydrated conidial mass, thereby extruding spores apically. We contrast these findings with previous suggestions that campylidia act as splash cups.
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Líquens/fisiologia , Dispersão de Sementes/fisiologia , Água/química , DessecaçãoRESUMO
It is widely understood that Hominoidea (apes and humans) and Cercopithecoidea (Old World monkeys) have a common ancestry as Catarrhini deeply rooted in Afro-Arabia. The oldest stem Catarrhini in the fossil record are Propliopithecoidea, known from the late Eocene to early Oligocene epochs (roughly 35-30 Myr ago) of Egypt, Oman and possibly Angola. Genome-based estimates for divergence of hominoids and cercopithecoids range into the early Oligocene; however, the mid-to-late Oligocene interval from 30 to 23 Myr ago has yielded little fossil evidence documenting the morphology of the last common ancestor of hominoids and cercopithecoids, the timing of their divergence, or the relationship of early stem and crown catarrhines. Here we describe the partial cranium of a new medium-sized (about 15-20 kg) fossil catarrhine, Saadanius hijazensis, dated to 29-28 Myr ago. Comparative anatomy and cladistic analysis shows that Saadanius is an advanced stem catarrhine close to the base of the hominoid-cercopithecoid clade. Saadanius is important for assessing competing hypotheses about the ancestral morphotype for crown catarrhines, early catarrhine phylogeny and the age of hominoid-cercopithecoid divergence. Saadanius has a tubular ectotympanic but lacks synapomorphies of either group of crown Catarrhini, and we infer that the hominoid-cercopithecoid split happened later, between 29-28 and 24 Myr ago.
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Cercopithecidae/classificação , Fósseis , Hominidae/classificação , Filogenia , Primatas/classificação , Animais , Tamanho Corporal , Cercopithecidae/anatomia & histologia , Geografia , História Antiga , Hominidae/anatomia & histologia , Humanos , Primatas/anatomia & histologia , Arábia Saudita , Crânio/anatomia & histologiaRESUMO
Foliicolous lichens are formed by diverse, highly specialized fungi that establish themselves and complete their life cycle within the brief duration of their leaf substratum. Over half of these lichen-forming fungi are members of either the Gomphillaceae or Pilocarpaceae, and associate with Trebouxia-like green algae whose identities have never been positively determined. We investigated the phylogenetic affinities of these photobionts to better understand their role in lichen establishment on an ephemeral surface. Thallus samples of Gomphillaceae and Pilocarpaceae were collected from foliicolous communities in southwest Florida and processed for sequencing of photobiont marker genes, algal cultivation and/or TEM. Additional specimens from these families and also from Aspidothelium (Thelenellaceae) were collected from a variety of substrates globally. Sequences from rbcL and nuSSU regions were obtained and subjected to Maximum Likelihood and Bayesian analyses. Analysis of 37 rbcL and 7 nuSSU algal sequences placed all photobionts studied within the provisional trebouxiophycean assemblage known as the Watanabea clade. All but three of the sequences showed affinities within Heveochlorella, a genus recently described from tree trunks in East Asia. The photobiont chloroplast showed multiple thylakoid stacks penetrating the pyrenoid centripetally as tubules lined with pyrenoglobuli, similar to the two described species of Heveochlorella. We conclude that Heveochlorella includes algae of potentially major importance as lichen photobionts, particularly within (but not limited to) foliicolous communities in tropical and subtropical regions worldwide. The ease with which they may be cultivated on minimal media suggests their potential to thrive free-living as well as in lichen symbiosis.
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Clorófitas/classificação , Clorófitas/fisiologia , Líquens/fisiologia , Filogenia , Simbiose , Proteínas de Algas/genética , Clorófitas/genética , DNA de Algas/genética , Florida , Análise de Sequência de DNARESUMO
PREMISE OF THE STUDY: Nondeciduous leaves of warm, humid climates can host highly specialized communities of diminutive lichens. The rarely reported Gyalectidium paolae, locally abundant on palm leaves in southwest Florida, may reproduce when as small as 0.15 mm diameter. We examined structural and developmental features to better understand the lifestyle of this extreme ephemeral. METHODS: Blocks containing resin-embedded thalli were sectioned and examined with TEM and SEM-BSE. Propagule development was studied with light microscopy applied to inoculated and naturally colonized plastic coverslips placed in the field. KEY RESULTS: Thallus areolae showed a heterogeneous covering that varied from cellular cortex to a simpler structure derived from fungal wall materials and sparse fungal cells of reduced diameter. Plates of crystalline deposits seemed to interrupt thallus structure, elevating the surface layer. No organized algal layer was present. Symbiont interactions were limited to appositional wall contacts with no haustorial penetration observed. Symbiotic propagules germinated promptly, but relative growth of fungal vs. algal components varied considerably. Smaller photobiont cells released from sporangia were present at the periphery of the thallus, or escaped to some distance. Fully formed hyphophores with abundant propagules appeared within 5 months, although there was evidence that propagule formation in Gyalectidium might occur much sooner. CONCLUSIONS: Gyalectidium paolae builds relatively simple thalli with limited fungal structure, prioritizing rapid formation of asexual propagules. Codispersal of algal symbionts permitted propagules to develop directly into thalli, but microenvironmental conditions may strongly influence survival and developmental equilibrium between the two symbionts necessary for success as a lichen.