Your browser doesn't support javascript.
loading
Montrer: 20 | 50 | 100
Résultats 1 - 20 de 22
Filtrer
1.
Eur Rev Med Pharmacol Sci ; 27(20): 9872-9879, 2023 Oct.
Article de Anglais | MEDLINE | ID: mdl-37916354

RÉSUMÉ

OBJECTIVE: Acute kidney injury (AKI) increases mortality and costs in hospitalized patients. New methods for early AKI identification have been developed with targeted biomarkers and electronic health records data analysis. Machine learning (ML) use in diagnostics and health data analysis has recently increased. We performed a systematic review to analyze the use of ML for AKI prediction in hospitalized adults. MATERIALS AND METHODS: Tubmed, EMBASE, Cochrane, and Web of Science databases were searched until 31st March of 2023. English-language studies using ML in adults for AKI prediction were included using predetermined eligibility search terms such as acute kidney injury, machine learning, and artificial intelligence. Two reviewers evaluated the publications' titles, abstracts, and full texts separately and obtained appropriate data. The main outcome was an area under the curve (AUC) result of at least 0.70. RESULTS: Ten studies in 102 articles were included involving 242,251 patients. Deep learning (AUC 0.907 in critical care AKI; AUC 0.797 in hospitalized patients AKI) was similar to Logistic regression (AUC 0.877 in critical care AKI; AUC 0.789 in hospitalized patients). Decision tree constructions had similar AUC. CONCLUSIONS: In this review, most ML models analyzed fulfilled the main outcome. AKI is multifactorial; however, ML performed well with different etiologies, such as cardiac-related AKI, drug-related AKI, and critical care patients. Overfitting data and constructing black box models are limitations that might jeopardize the generalization and comprehension of the results. Most studies were single-center, and three manuscripts used the same database with a predominantly Caucasian population, resulting in a lack of diversity and reducing external generalization. In conclusion, ML could effectively predict AKI in hospitalized adults. Future directions rely on including a more diverse population and completing prospective and controlled trials.


Sujet(s)
Atteinte rénale aigüe , Intelligence artificielle , Adulte , Humains , Études prospectives , Marqueurs biologiques , Apprentissage machine , Atteinte rénale aigüe/diagnostic , Atteinte rénale aigüe/étiologie
2.
Crit Care Res Pract ; 2023: 8403971, 2023.
Article de Anglais | MEDLINE | ID: mdl-37766780

RÉSUMÉ

Introduction: Daily evaluation of mechanically ventilated (MV) patients is essential for successful extubation. Proper withdrawal prevents complications and reduces the cost of hospitalization in the intensive care unit (ICU). Diaphragm ultrasonography (DUS) has emerged as a potential instrument for determining whether a patient is ready to be extubated. This study compared the efficacy rate of extubation using a standard withdrawal protocol and DUS in patients with MV. Methods: A randomized, parallel, single-blind, controlled study was conducted on ICU patients undergoing MV. Patients were randomly assigned to either the control (conventional weaning protocol) group or intervention (DUS-guided weaning) group in a 1 : 1 ratio. The primary outcome measure was the rate of reintubation and hospital mortality. Results: Forty patients were randomized to the trial. The mean age of the sample was 70 years, representing an older population. The extubation success rate was 90% in both groups. There was no reintubation in the first 48 hours and only two reintubations in both groups between the second and seventh days. The hospital mortality risk in patients with acute kidney injury was positively correlated with age and the need for hemodialysis. Discussion. This study demonstrates the usefulness of DUS measurement protocols for withdrawing MV. The rate of reintubation was low for both cessation methods. As a parameter, the diaphragm thickness fraction comprehensively evaluates the diaphragm function. The results demonstrate that DUS has the potential to serve as a noninvasive tool for guiding extubation decisions. In conclusion, using DUS in patients with respiratory failure revealed no difference in reintubation rates or mortality compared with the conventional method. Future research should concentrate on larger, multicentered, randomized trials employing a multimodal strategy that combines diaphragmatic parameters with traditional clinical withdrawal indices.

3.
Braz J Med Biol Res ; 51(6): e7355, 2018.
Article de Anglais | MEDLINE | ID: mdl-29694512

RÉSUMÉ

Chronic kidney disease (CKD) is highly prevalent worldwide. Patients with CKD on hemodialysis are more likely to present behavioral changes and worse quality of life as a result of their routine and complications. They also have higher levels of cytokines. The aim of this study is to assess the relationship between the inflammatory profile and quality of life measured by KDOQL-SF36 in hemodialysis outpatients. Patients older than 21 years of age and on routine hemodialysis for at least 6 months with treatment on a regular weekly basis were included and their anthropometric parameters and serum inflammatory markers were evaluated. Thirty patients consented to participate. Homocysteine (Hcy) levels were correlated with worse glomerular filtration rate (GFR; P=0.003) and creatinine (P=0.002). IL-6 was not correlated with worse nutritional status taking into account body mass index (BMI; kg/m2; P=0.83). On the other hand, TNF-alpha was positively correlated with albumin (P=0.008), nutritional status by BMI (P=0.04), and nutritional status by arm circumference area (P=0.04). IL-6 was correlated with activity limitation (P=0.02) and Hcy with work status (P=0.04). Hcy was correlated with nutritional status and inflammatory markers. In this population, the majority of the sections in KDOQL-SF36 were not correlated with cytokines levels.


Sujet(s)
Marqueurs biologiques/sang , Inflammation/sang , Qualité de vie/psychologie , Dialyse rénale/psychologie , Insuffisance rénale chronique/thérapie , Adulte , Indice de masse corporelle , Créatinine/sang , Cytokines/sang , Femelle , Débit de filtration glomérulaire , Homocystéine/sang , Humains , Inflammation/étiologie , Mâle , État nutritionnel , Dialyse rénale/effets indésirables , Insuffisance rénale chronique/sang , Sérumalbumine/analyse , Enquêtes et questionnaires , Facteur de nécrose tumorale alpha/sang
4.
Eur Rev Med Pharmacol Sci ; 20(19): 4072-4077, 2016 10.
Article de Anglais | MEDLINE | ID: mdl-27775791

RÉSUMÉ

OBJECTIVE: Irisin is a muscle-secreted protein released into the circulation by cleavage of fibronectin type III domain containing protein 5(FNDC5). Since its discovery in 2012, it has been the subject of many researches due to its physiological role. It is believed that understanding irisin's function may be the key to comprehend many diseases and their development. The aim of this study is to perform a systematic review in order to establish whether there is an association of irisin's levels with obesity, diabetes mellitus, non-alcoholic steatohepatitis, chronic kidney disease and cancer in terms of prognosis. MATERIALS AND METHODS: The articles that support these findings were selected from Medline using the keyword "irisin" and filtered with "humans only". The selected articles were in English and with abstract. RESULTS: Higher baseline irisin concentrations are associated with greater reductions in glycemia and insulinemia after weight loss in obese subjects. Besides, it was observed that macrovascular disease, a complication of diabetes, was developed when there were lower levels of irisin. In addition, although not statistically significant, high levels of irisin were associated with portal inflammation and severity of histological lesions. Its concentrations decreased with increasing chronic kidney disease stage, and they were not only independently and positively predicted by renal function and insulin resistance but also associated with sarcopenia and carotid atherosclerosis in patients undergoing peritoneal dialysis. Regarding cancer, irisin reduced the proliferation, viability and migration of malignant breast cells. Finally, it is also related to bone health once its concentration is associated with previous osteoporotic fractures. CONCLUSIONS: In every condition studied, irisin's concentrations were related to the development of the disease.


Sujet(s)
Maladie chronique , Fibronectines/métabolisme , Insulinorésistance , Humains , Obésité , Pronostic , Sarcopénie
5.
Antonie Van Leeuwenhoek ; 109(9): 1235-43, 2016 Sep.
Article de Anglais | MEDLINE | ID: mdl-27307255

RÉSUMÉ

The relationship of attine ants with their mutualistic fungus and other microorganisms has been studied during the last two centuries. However, previous studies about the diversity of fungi in the ants' microenvironment are based mostly on culture-dependent approaches, lacking a broad characterization of the fungal ant-associated community. Here, we analysed the fungal diversity found on the integument of Atta capiguara and Atta laevigata alate ants using 454 pyrosequencing. We obtained 35,453 ITS reads grouped into 99 molecular operational taxonomic units (MOTUs). Data analysis revealed that A. capiguara drones had the highest diversity of MOTUs. Besides the occurrence of several uncultured fungi, the mycobiota analysis revealed that the most abundant taxa were the Cladosporium-complex, Cryptococcus laurentii and Epicoccum sp. Taxa in the genus Cladosporium were predominant in all samples, comprising 67.9 % of all reads. The remarkable presence of the genus Cladosporium on the integument of leaf-cutting ants alates from distinct ant species suggests that this fungus is favored in this microenvironment.


Sujet(s)
Fourmis/microbiologie , Cladosporium/isolement et purification , Animaux , Biodiversité , Brésil , Cladosporium/classification , Cladosporium/génétique , ADN fongique/génétique , Espaceur de l'ADN ribosomique/génétique , Système tégumentaire/microbiologie , Mycobiome , Prévalence , Analyse de séquence d'ADN , Peau/microbiologie , Symbiose
6.
Mol Ecol Resour ; 16(4): 1012-22, 2016 Jul.
Article de Anglais | MEDLINE | ID: mdl-26849180

RÉSUMÉ

We present the leaf and floral transcriptomes of two hybridizing bromeliad species that differ in their major pollinator systems. Here we identified candidate genes responsible for pollinator attraction and reproductive isolation in these two species. We searched for candidate genes involved in floral traits, such as colour. Approximately 34 Gbp of cDNA sequence data were produced from both tissues and species, resulting in a total of 424 506 914 raw reads. The de novo-assembled transcriptomes consisted of a total of 263 955 contigs, further clustered into 110 977 unigenes. Over 58% of the unigenes were functionally annotated and assigned to one or more Gene Ontology terms. The transcriptomes revealed 144 unique transcripts that encode key enzymes in the flavonoid and anthocyanin biosynthesis pathways. The domain/family annotation and phylogenetic analysis allowed us to infer, by homology, potential functions of the genes encoding MYB, HD-ZIP and bZIP-HY5 transcription factors, as well as WD40 protein, which may be involved in anthocyanin and flavonoid regulation in these species. These candidate genes are associated with natural regulation in flower colour in other plant species and will facilitate future studies aimed at elucidating the molecular basis of adaptive differentiation and the evolution of mechanisms of pollinator-mediated reproductive isolation in these two bromeliads. In addition, we identified a total of 49 439 microsatellite loci. These resources will assist future research into adaptation and speciation events in bromeliad species, thus providing a starting point for investigation of the molecular mechanisms of the traits responsible for their reproductive isolation.


Sujet(s)
Bromeliaceae/génétique , Fleurs/génétique , Variation génétique , Feuilles de plante/génétique , Transcriptome , Adaptation biologique , Bromeliaceae/classification , Évolution moléculaire , Régulation de l'expression des gènes végétaux , Gènes de plante , Études d'associations génétiques , Annotation de séquence moléculaire , Analyse de séquence d'ADN , Climat tropical
7.
Rev. bras. pesqui. méd. biol ; Braz. j. med. biol. res;48(5): 427-432, 05/2015. tab
Article de Anglais | LILACS | ID: lil-744368

RÉSUMÉ

Community-acquired pneumonia (CAP) is amongst the leading causes of death worldwide. As inflammatory markers, cytokines can predict outcomes, if interpreted together with clinical data and scoring systems such as CURB-65, CRB, and Acute Physiology and Chronic Health Evaluation II (APACHE II). The aim of this study was to determine the impact of inflammatory biomarkers on the early mortality of hospitalized CAP patients. Twenty-seven CAP patients needing hospitalization were enrolled for the study and samples of interleukin-1 (IL-1) and interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), C-reactive protein (CRP), and homocystein were collected at the time of admission (day 1) as well as on the seventh day of the treatment. There was a significant reduction in the levels of IL-6 between the first and the second collections. Median IL-6 values decreased from 24 pg/mL (day 1) to 8 pg/mL (day 7) (P=0.016). The median levels of TNF-α were higher in patients: i) with acute kidney injury (AKI) (P=0.045), ii) requiring mechanical ventilation (P=0.040), iii) with short hospital stays (P=0.009), iv) admitted to the intensive care unit (ICU) (P=0.040), v) who died early (P=0.003), and vi) with worse CRB scores (P=0.013). In summary, IL-6 and TNF-α levels were associated with early mortality of CAP patients. Longer admission levels demonstrated greater likelihood of early death and overall mortality, necessity of mechanical ventilation, and AKI.


Sujet(s)
Adolescent , Humains , Financement du gouvernement , Centres de traitement de la toxicomanie/organisation et administration , Troubles liés à une substance/rééducation et réadaptation , Bases de données factuelles , Assurance de la qualité des soins de santé , Qualité des soins de santé , Centres de traitement de la toxicomanie/normes , Centres de traitement de la toxicomanie/tendances , États-Unis
8.
Eur Rev Med Pharmacol Sci ; 19(4): 694-700, 2015 Feb.
Article de Anglais | MEDLINE | ID: mdl-25753888

RÉSUMÉ

OBJECTIVE: Vancomycin (VCM) is a tricyclic glycopeptide antibiotic produced by Streptococcus orientalis. Widely used in hospitals, it is indicated to fight severe infections caused by Gram-positive bacteria, especially with the advent of MRSA (methicillin-resistant Staphylococcus aureus), penicillin-resistant pneumococci among others. Furthermore, it is indicated for the treatment of patients allergic to penicillins and cephalosporins. Dose recommendations, dilution rates and types of infusion are controversial and also result in toxic effects. Aim of this paper was to perform a literature review showing the therapeutic and adverse effects of vancomycin. MATERIALS AND METHODS: This is a literature review of recent articles published on MEDLINE and SciELO databases in English, Portuguese and Spanish. RESULTS: The main adverse effects of vancomycin are: hypotension, phlebitis, nephrotoxicity, ototoxicity, hypersensitivity reactions, red man syndrome, neutropenia, chills, fever, interstitial nephritis. CONCLUSIONS: The use of vancomycin is still very common; however, inadequate doses and prolonged therapy pose a risk of increasing minimum inhibitory concentrations (MICs), resulting in subtherapeutic levels, treatment failures and toxicity. Therefore, further studies should be conducted to optimize the administration of vancomycin, monitoring treatments from the beginning in order to ensure a safe and effective use of the drug.


Sujet(s)
Antibactériens/effets indésirables , Antibactériens/usage thérapeutique , Infections bactériennes à Gram positif/traitement médicamenteux , Vancomycine/effets indésirables , Vancomycine/usage thérapeutique , Céphalosporines/usage thérapeutique , Bactéries à Gram positif/effets des médicaments et des substances chimiques , Humains , Staphylococcus aureus résistant à la méticilline/effets des médicaments et des substances chimiques , Tests de sensibilité microbienne , Neutropénie/induit chimiquement
9.
Braz J Med Biol Res ; 48(5): 427-32, 2015 May.
Article de Anglais | MEDLINE | ID: mdl-25714883

RÉSUMÉ

Community-acquired pneumonia (CAP) is amongst the leading causes of death worldwide. As inflammatory markers, cytokines can predict outcomes, if interpreted together with clinical data and scoring systems such as CURB-65, CRB, and Acute Physiology and Chronic Health Evaluation II (APACHE II). The aim of this study was to determine the impact of inflammatory biomarkers on the early mortality of hospitalized CAP patients. Twenty-seven CAP patients needing hospitalization were enrolled for the study and samples of interleukin-1 (IL-1) and interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), C-reactive protein (CRP), and homocystein were collected at the time of admission (day 1) as well as on the seventh day of the treatment. There was a significant reduction in the levels of IL-6 between the first and the second collections. Median IL-6 values decreased from 24 pg/mL (day 1) to 8 pg/mL (day 7) (P=0.016). The median levels of TNF-α were higher in patients: i) with acute kidney injury (AKI) (P=0.045), ii) requiring mechanical ventilation (P=0.040), iii) with short hospital stays (P=0.009), iv) admitted to the intensive care unit (ICU) (P=0.040), v) who died early (P=0.003), and vi) with worse CRB scores (P=0.013). In summary, IL-6 and TNF-α levels were associated with early mortality of CAP patients. Longer admission levels demonstrated greater likelihood of early death and overall mortality, necessity of mechanical ventilation, and AKI.


Sujet(s)
Interleukine-6/sang , Pneumopathie infectieuse/mortalité , Facteur de nécrose tumorale alpha/sang , Adolescent , Adulte , Facteurs âges , Sujet âgé , Sujet âgé de 80 ans ou plus , Marqueurs biologiques/sang , Protéine C-réactive/analyse , Enfant , Enfant d'âge préscolaire , Infections communautaires/complications , Infections communautaires/mortalité , Créatinine/sang , Femelle , Homocystéine/sang , Humains , Nourrisson , Nouveau-né , Interleukine-1/sang , Durée du séjour , Mâle , Adulte d'âge moyen , Pneumopathie infectieuse/complications , Études prospectives , Ventilation artificielle , Facteurs sexuels , Statistique non paramétrique , Jeune adulte
10.
11.
Clin Biochem ; 46(15): 1622-4, 2013 Oct.
Article de Anglais | MEDLINE | ID: mdl-23769952

RÉSUMÉ

OBJECTIVES: Infection caused by Helicobacter pylori (H. pylori) is one of the most common causes of chronic infection in the world. The presence of the infection is strongly associated with the neoplasia of the gastrointestinal tract, and its diagnosis is easily made by means of invasive or non-invasive methods. Among such methods, the H. pylori antigen detection in stool through ELISA technique is easily performed and it is an alternative to endoscopy in children, since this exam is not usually indicated in this age group. The aim of the current study is to establish the standardization of the ELISA method for the detection of H. pylori in stool specimens in Brazil. DESIGN AND METHODS: Patients between 18 and 70 years of age were randomly selected in the gastroenterology ambulatory center at Faculdade de Medicina do ABC between 2007 and 2009. They all answered a questionnaire to investigate possible dyspeptic symptoms and then underwent endoscopy and detection of H. pylori through no more than 4 methods. Besides the gastric biopsy, established as the gold standard test, the urease test, the stool ELISA test and serology were also methods applied. RESULTS: The sensitivity and specificity of the exams in this sample were respectively 87.2% and 44% for the stool ELISA test, 41.9% and 64% for serology, 65.6% and 58.8% for the urease test and 100% and 80.8% for the clinical analysis. CONCLUSIONS: The ROC curve showed a good correlation between the compared methods. In Brazil the standardization of the ELISA test for the detection of H. pylori in stool specimens constitutes a non-invasive diagnostic alternative.


Sujet(s)
Test ELISA/normes , Fèces/microbiologie , Infections à Helicobacter/diagnostic , Helicobacter pylori/isolement et purification , Adolescent , Adulte , Antigènes bactériens/sang , Protéines bactériennes/analyse , Biopsie , Brésil , Test ELISA/méthodes , Femelle , Infections à Helicobacter/microbiologie , Helicobacter pylori/immunologie , Humains , Mâle , Adulte d'âge moyen , Sensibilité et spécificité , Urease/analyse
12.
Braz J Med Biol Res ; 44(9): 855-63, 2011 Sep.
Article de Anglais | MEDLINE | ID: mdl-21956531

RÉSUMÉ

The health-promoting effects of exercise training (ET) are related to nitric oxide (NO) production and/or its bioavailability. The objective of this study was to determine whether single nucleotide polymorphism of the endothelial NO synthase (eNOS) gene at positions -786T>C, G894T (Glu298Asp) and at the variable number of tandem repeat (VNTR) Intron 4b/a would interfere with the cardiometabolic responses of postmenopausal women submitted to physical training. Forty-nine postmenopausal women were trained in sessions of 30-40 min, 3 days a week for 8 weeks. Genotypes, oxidative stress status and cardiometabolic parameters were then evaluated in a double-blind design. Both systolic and diastolic blood pressure values were significantly reduced after ET, which was genotype-independent. However, women without eNOS gene polymorphism at position -786T>C (TT genotype) and Intron 4b/a (bb genotype) presented a better reduction of total cholesterol levels (-786T>C: before = 213 ± 12.1, after = 159.8 ± 14.4, Δ = -24.9% and Intron 4b/a: before = 211.8 ± 7.4, after = 180.12 ± 6.4 mg/dL, Δ = -15%), and LDL cholesterol (-786T>C: before = 146.1 ± 13.3, after = 82.8 ± 9.2, Δ = -43.3% and Intron 4b/a: before = 143.2 ± 8, after = 102.7 ± 5.8 mg/dL, Δ = -28.3%) in response to ET compared to those who carried the mutant allele. Superoxide dismutase activity was significantly increased in trained women whereas no changes were observed in malondialdehyde levels. Women without eNOS gene polymorphism at position -786T>C and Intron 4b/a showed a greater reduction of plasma cholesterol levels in response to ET. Furthermore, no genotype influence was observed on arterial blood pressure or oxidative stress status in this population.


Sujet(s)
Exercice physique/physiologie , Nitric oxide synthase type III/génétique , Polymorphisme de nucléotide simple , Post-ménopause/génétique , Post-ménopause/métabolisme , Pression sanguine/physiologie , Loi du khi-deux , Méthode en double aveugle , Femelle , Génotype , Humains , Lipides/sang , Malonaldéhyde/sang , Adulte d'âge moyen , Répétitions minisatellites/génétique , Stress oxydatif/physiologie , Facteurs temps
13.
Rev. bras. pesqui. méd. biol ; Braz. j. med. biol. res;44(9): 855-863, Sept. 2011. ilus, tab
Article de Anglais | LILACS | ID: lil-599675

RÉSUMÉ

The health-promoting effects of exercise training (ET) are related to nitric oxide (NO) production and/or its bioavailability. The objective of this study was to determine whether single nucleotide polymorphism of the endothelial NO synthase (eNOS) gene at positions -786T>C, G894T (Glu298Asp) and at the variable number of tandem repeat (VNTR) Intron 4b/a would interfere with the cardiometabolic responses of postmenopausal women submitted to physical training. Forty-nine postmenopausal women were trained in sessions of 30-40 min, 3 days a week for 8 weeks. Genotypes, oxidative stress status and cardiometabolic parameters were then evaluated in a double-blind design. Both systolic and diastolic blood pressure values were significantly reduced after ET, which was genotype-independent. However, women without eNOS gene polymorphism at position -786T>C (TT genotype) and Intron 4b/a (bb genotype) presented a better reduction of total cholesterol levels (-786T>C: before = 213 ± 12.1, after = 159.8 ± 14.4, Δ = -24.9 percent and Intron 4b/a: before = 211.8 ± 7.4, after = 180.12 ± 6.4 mg/dL, Δ = -15 percent), and LDL cholesterol (-786T>C: before = 146.1 ± 13.3, after = 82.8 ± 9.2, Δ = -43.3 percent and Intron 4b/a: before = 143.2 ± 8, after = 102.7 ± 5.8 mg/dL, Δ = -28.3 percent) in response to ET compared to those who carried the mutant allele. Superoxide dismutase activity was significantly increased in trained women whereas no changes were observed in malondialdehyde levels. Women without eNOS gene polymorphism at position -786T>C and Intron 4b/a showed a greater reduction of plasma cholesterol levels in response to ET. Furthermore, no genotype influence was observed on arterial blood pressure or oxidative stress status in this population.


Sujet(s)
Femelle , Humains , Adulte d'âge moyen , Exercice physique/physiologie , Nitric oxide synthase type III/génétique , Polymorphisme de nucléotide simple , Post-ménopause/génétique , Post-ménopause/métabolisme , Pression sanguine/physiologie , Loi du khi-deux , Méthode en double aveugle , Génotype , Lipides/sang , Malonaldéhyde/sang , Répétitions minisatellites/génétique , Stress oxydatif/physiologie , Facteurs temps
14.
Microb Ecol ; 56(4): 604-14, 2008 Nov.
Article de Anglais | MEDLINE | ID: mdl-18369523

RÉSUMÉ

Leafcutter ants (Formicidae: tribe Attini) are well-known insects that cultivate basidiomycete fungi (Agaricales: Lepiotaceae) as their principal food. Fungus gardens are monocultures of a single cultivar strain, but they also harbor a diverse assemblage of additional microbes with largely unknown roles in the symbiosis. Cultivar-attacking microfungi in the genus Escovopsis are specialized parasites found only in association with attine gardens. Evolutionary theory predicts that the low genetic diversity in monocultures should render ant gardens susceptible to a wide range of diseases, and additional parasites with roles similar to that of Escovopsis are expected to exist. We profiled the diversity of cultivable microfungi found in 37 nests from ten Acromyrmex species from Southern Brazil and compared this diversity to published surveys. Our study revealed a total of 85 microfungal strains. Fusarium oxysporum and Escovopsis were the predominant species in the surveyed gardens, infecting 40.5% and 27% of the nests, respectively. No specific relationship existed regarding microfungal species and ant-host species, ant substrate preference (dicot versus grass) or nesting habit. Molecular data indicated high genetic diversity among Escovopsis isolates. In contrast to the garden parasite, F. oxysporum strains are not specific parasites of the cultivated fungus because strains isolated from attine gardens have similar counterparts found in the environment. Overall, the survey indicates that saprophytic microfungi are prevalent in South American leafcutter ants. We discuss the antagonistic potential of these microorganisms as "weeds" in the ant-fungus symbiosis.


Sujet(s)
Agaricales/croissance et développement , Fourmis/microbiologie , Symbiose , Agaricales/classification , Agaricales/génétique , Animaux , Variation génétique , Données de séquences moléculaires , Phylogenèse
15.
Insect Mol Biol ; 16(6): 777-84, 2007 Dec.
Article de Anglais | MEDLINE | ID: mdl-18093006

RÉSUMÉ

Nuclear mitochondrial-like sequences (numts) are copies of mitochondrial DNA that have migrated to the genomic DNA. We present the first characterization of numts in ants, these numts being homologues to a mitochondrial DNA fragment containing loci the 3' portion of the cytochrome oxidase I gene, an intergenic spacer, the tRNA leucine gene and the 5' portion of the cytochrome oxidase II gene. All 67 specimens of Atta cephalotes (Hymenoptera: Formicidae: Attini) investigated had these homologues, which are within two monophyletic groups that we called numt1 and numt2. Numt1 and numt2 sequences are less variable than mitochondrial sequences and released from the severe purifying selection constraining the evolution of mitochondrial genes. Their formation probably involved bottlenecks related to two distinct transfer events of ancient and fast evolving mitochondrial DNA fragments to comparative slowly evolving nuclear DNA regions.


Sujet(s)
Fourmis/génétique , ADN mitochondrial/génétique , Séquence d'acides aminés , Animaux , Fourmis/enzymologie , Séquence nucléotidique , Noyau de la cellule/génétique , ADN/génétique , Amorces ADN/génétique , Complexe IV de la chaîne respiratoire/génétique , Gènes d'insecte , Données de séquences moléculaires , Phylogenèse , Similitude de séquences d'acides aminés
16.
Mycopathologia ; 162(2): 115-9, 2006 Aug.
Article de Anglais | MEDLINE | ID: mdl-16897590

RÉSUMÉ

The aim of this study was to select virulent strains of microfungi against Leucoagaricus gongylophorus, a symbiotic fungus cultivated by leaf-cutting ants. The results from in vitro assays showed that microfungal strains had a variable and significant impact on the colony development of L. gongylophorus. Specifically, Trichoderma harzianum, Escovopsis weberi CBS 810.71 and E. weberi A088 were more effective, inhibiting the L. gongylophorus colonies by 75, 68 and 67%, respectively (P < 0.05) after 15 days. Strain E. weberi A086 and Acremonium kiliense were less effective: 43 and 26%, respectively (P < 0.05). In spite of the current negative perspective of a microbiological control approach for these ants, the present work discusses the possibility of using mycopathogenic fungi for the control of these insects, and points out the importance of encouraging more studies in this area.


Sujet(s)
Fourmis/microbiologie , Basidiomycota/physiologie , Lutte contre les insectes/méthodes , Deuteromycota/physiologie , Animaux , Basidiomycota/cytologie , Deuteromycota/cytologie , Symbiose
17.
Microbiol Res ; 161(4): 299-303, 2006.
Article de Anglais | MEDLINE | ID: mdl-16380244

RÉSUMÉ

Leucoagaricus gongylophorus, the symbiotic fungus of the leaf-cutting ants, degrades starch, this degradation being supposed to occur in the plant material which leafcutters forage to the nests, generating most of the glucose which the ants utilize for food. In the present investigation, we show that laboratory cultures of L. gongylophorus produce extracellular alpha-amylase and maltase which degrade starch to glucose, reinforcing that the ants can obtain glucose from starch through the symbiotic fungus. Glucose was found to repress alpha-amylase and, more severely, maltase activity, thus repressing starch degradation by L. gongylophorus, so that we hypothesize that: (1) glucose down-regulation of starch degradation also occurs in the Atta sexdens fungus garden; (2) glucose consumption from the fungus garden by A. sexdens stimulates degradation of starch from plant material by L. gongylophorus, which may represent a mechanism by which leafcutters can control enzyme production by the symbiotic fungus. Since glucose is found in the fungus garden inside the nests, down-regulation of starch degradation by glucose is supposed to occur in the nest and play a part in the control of fungal enzyme production by leafcutters.


Sujet(s)
Agaricales/enzymologie , Agaricales/métabolisme , Fourmis/microbiologie , Amidon/métabolisme , Symbiose , Agaricales/physiologie , Animaux , Fourmis/physiologie , Feuilles de plante/parasitologie
18.
Folia Microbiol (Praha) ; 50(5): 421-5, 2005.
Article de Anglais | MEDLINE | ID: mdl-16475502

RÉSUMÉ

A survey of the filamentous fungi other than the symbiotic one found in association with Atta sexdens rubropilosa colonies was carried out. Different fungal species (27 taxa) were isolated a few days after treating the workers with toxic baits (sulfluramid; Mirex-S), from 40 laboratory and 20 field nests. Syncephalastrum racemosum (54%) and Escovopsis weberi (21%), Trichoderma harzianum (38%) and Fusarium oxysporum (23%) were the prevalent species in laboratory and field nests, respectively. Acremonium kiliense, Acremonium strictum, E. weberi, F. oxysporum, Fusarium solani, Moniliella suaveolens and T. harzianum were found in both nests' groups. We revealed that many filamentous fungi can co-exist in a dormant state inside the nests of these insects and some of them appear to be tightly associated with this environment.


Sujet(s)
Champignons/classification , Champignons/isolement et purification , Hymenoptera/microbiologie , Microbiologie du sol , Animaux , Champignons/croissance et développement , Symbiose
19.
Braz J Med Biol Res ; 37(10): 1463-72, 2004 Oct.
Article de Anglais | MEDLINE | ID: mdl-15448866

RÉSUMÉ

Leaf-cutting ants of the genera Atta and Acromyrmex (tribe Attini) are symbiotic with basidiomycete fungi of the genus Leucoagaricus (tribe Leucocoprineae), which they cultivate on vegetable matter inside their nests. We determined the variation of the 28S, 18S, and 5.8S ribosomal DNA (rDNA) gene loci and the rapidly evolving internal transcribed spacers 1 and 2 (ITS1 and ITS2) of 15 sympatric and allopatric fungi associated with colonies of 11 species of leafcutter ants living up to 2,600 km apart in Brazil. We found that the fungal rDNA and ITS sequences from different species of ants were identical (or nearly identical) to each other, whereas 10 GenBank Leucoagaricus species showed higher ITS variation. Our findings suggest that Atta and Acromyrmex leafcutters living in geographic sites that are very distant from each other cultivate a single fungal species made up of closely related lineages of Leucoagaricus gongylophorus. We discuss the strikingly high similarity in the ITS1 and ITS2 regions of the Atta and Acromyrmex symbiotic L. gongylophorus studied by us, in contrast to the lower similarity displayed by their non-symbiotic counterparts. We suggest that the similarity of our L. gongylophorus isolates is an indication of the recent association of the fungus with these ants, and propose that both the intense lateral transmission of fungal material within leafcutter nests and the selection of more adapted fungal strains are involved in the homogenization of the symbiotic fungal stock.


Sujet(s)
Fourmis/physiologie , Espaceur de l'ADN ribosomique/génétique , Champignons/génétique , Variation génétique , Symbiose , Animaux , Brésil , Champignons/physiologie , Feuilles de plante , Réaction de polymérisation en chaîne , Analyse de séquence d'ADN
20.
Folia Microbiol (Praha) ; 47(3): 259-62, 2002.
Article de Anglais | MEDLINE | ID: mdl-12099266

RÉSUMÉ

Killer activity was screened in 99 yeast strains isolated from the nests of the leaf-cutting ant Atta sexdens against 6 standard sensitive strains, as well as against each other. Among this yeast community killer activity was widespread since 77 strains (78%) were able to kill or inhibit the growth of at least one standard strain or nest strain. Toxin production was observed in representatives of all the studied genera including Aureobasidium, Rhodotorula, Tremella and Trichosporon, whose killer activity has not yet been described.


Sujet(s)
Fourmis/microbiologie , Levures/isolement et purification , Animaux , Milieux de culture , Concentration en ions d'hydrogène , Toxines tueuses de levure , Mycotoxines/analyse , Mycotoxines/isolement et purification , Phénotype , Rhodotorula/isolement et purification , Rhodotorula/métabolisme , Spécificité d'espèce , Trichosporon/isolement et purification , Trichosporon/métabolisme , Levures/classification , Levures/métabolisme
SÉLECTION CITATIONS
DÉTAIL DE RECHERCHE