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The choice to postpone treatment while awaiting genetic testing can result in significant delay in definitive therapies in patients with severe pancytopenia. Conversely, the misdiagnosis of inherited bone marrow failure (BMF) can expose patients to ineffectual and expensive therapies, toxic transplant conditioning regimens, and inappropriate use of an affected family member as a stem cell donor. To predict the likelihood of patients having acquired or inherited BMF, we developed a 2-step data-driven machine-learning model using 25 clinical and laboratory variables typically recorded at the initial clinical encounter. For model development, patients were labeled as having acquired or inherited BMF depending on their genomic data. Data sets were unbiasedly clustered, and an ensemble model was trained with cases from the largest cluster of a training cohort (n = 359) and validated with an independent cohort (n = 127). Cluster A, the largest group, was mostly immune or inherited aplastic anemia, whereas cluster B comprised underrepresented BMF phenotypes and was not included in the next step of data modeling because of a small sample size. The ensemble cluster A-specific model was accurate (89%) to predict BMF etiology, correctly predicting inherited and likely immune BMF in 79% and 92% of cases, respectively. Our model represents a practical guide for BMF diagnosis and highlights the importance of clinical and laboratory variables in the initial evaluation, particularly telomere length. Our tool can be potentially used by general hematologists and health care providers not specialized in BMF, and in under-resourced centers, to prioritize patients for genetic testing or for expeditious treatment.
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Anemia Aplásica , Enfermedades de la Médula Ósea , Pancitopenia , Humanos , Enfermedades de la Médula Ósea/diagnóstico , Enfermedades de la Médula Ósea/genética , Enfermedades de la Médula Ósea/terapia , Diagnóstico Diferencial , Anemia Aplásica/diagnóstico , Anemia Aplásica/genética , Anemia Aplásica/terapia , Trastornos de Fallo de la Médula Ósea/diagnóstico , Pancitopenia/diagnósticoRESUMEN
Telomere Biology Disorders (TBDs) are a group of rare diseases characterized by the presence of short and/or dysfunctional telomeres. They comprise a group of bone marrow failure syndromes, idiopathic pulmonary fibrosis, and liver disease, among other diseases. Genetic alterations (variants) in the genes responsible for telomere homeostasis have been linked to TBDs. Despite the number of variants already identified as pathogenic, an even more significant number must be better understood. The study of TBDs is challenging since identifying these variants is difficult due to their rareness, it is hard to predict their impact on the disease onset, and there are not enough samples to study. Most of our knowledge about pathogenic variants comes from assessing telomerase activity from patients and their relatives affected by a TBD. However, we still lack a cell-based model to identify new variants and to study the long-term impact of such variants on the genes involved in TBDs. Herein, we present a cell-based model using CRISPR base editing to mutagenize the endogenous alleles of 21 genes involved in telomere biology. We identified key residues in the genes encoding 17 different proteins impacting cell growth. We provide functional evidence for variants of uncertain significance in patients with TBDs. We also identified variants resistant to telomerase inhibition that, similar to cells expressing wild-type telomerase, exhibited increased tumorigenic potential using an in vitro tumour growth assay. We believe that such cell-based approaches will significantly advance our understanding of the biology of TBDs and may contribute to the development of new therapies for this group of diseases.
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Telomerasa , Humanos , Telomerasa/genética , Telomerasa/metabolismo , Repeticiones Palindrómicas Cortas Agrupadas y Regularmente Espaciadas , Edición Génica , Envejecimiento/genética , Telómero/genética , BiologíaRESUMEN
STATEMENT OF PROBLEM: Misfits at the implant-prosthesis interface may increase complications in dental implants and affect peri-implant tissue health. Periapical radiographs are the most used imaging examinations for detecting misfits at the implant-prosthesis interface, although digital systems have largely replaced film-based radiographs. Whether postprocessing tools such as enhancement filters assist diagnosis by highlighting misfits is unclear. PURPOSE: The purpose of this in vitro study was to assess the influence of enhancement filter application in the diagnostic accuracy of misfit detection at the implant-prosthesis interface. MATERIAL AND METHODS: A total of 32 dental implants were placed in dry human mandibles. A polyester strip was inserted at the implant-prosthesis interface to simulate a 50-µm misfit; prosthetic crowns installed directly on the implant platforms were used as controls. Standard paralleling periapical images were acquired by using a semidirect system (photostimulable phosphor plate) with the application of Highlight, Invert, and Colorization filters, as well as a direct system (metal oxide complementary semiconductor sensor) with filters Sharpness 3, Invert, and Pseudocolorization. Oral radiologists evaluated the images with and without the application of filters. The areas under the receiver operating characteristics curves (Az values), sensitivity, specificity, accuracy, positive predictive value, and negative predictive values were calculated. The Az values were compared with the receiver operating characteristic (ROC) curves comparison test of the Epidat 3.1 software (α=.05). RESULTS: Although images without filter application presented descriptively higher diagnostic values than those with filter application, the Az values for images with and without filter application in both semidirect and direct systems showed no significant differences (P>.05). CONCLUSIONS: Enhancement filter application did not significantly influence the diagnostic accuracy of misfit detection at the implant-prosthesis interface.
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Background: In the pubertal period, each part of the body grows at different rates. This makes the relationship between the parts nonlinear. Particularly, the fat mass (FM) of boys tends to decrease, further exacerbating the issue of linearity in growth.Aim: To propose predictive models of FM from skinfolds (SF) adjusted allometrically.Subjects and methods: 75 pubertal boys (14.4 ± 0.9 years) composed the sample by self-selected pubic hair. FM was determined by DXA (FMDXA) (kg), stature (cm), body mass (kg) and nine SF (mm) by anthropometric measurements. The SF were individually adjusted allometrically. FMDXA (Y) values and each anthropometric independent variable-IV (X) underwent logarithmic transformation. Linear regressions were used. The significance of the prediction of the FMDXA of each model (ANOVA) and the concordance analysis (Bland-Altman) were performed.Results: Predictive allometric models of FMDXA showed high determination coefficients (r2) and reduced standard errors of estimation (SEE). The adjusted model involved reduced agreement limits, demonstrating its accuracy.Conclusions: It was possible to propose models with allometric adjustments to estimate FM of pubertal boys. Allometry may aid in the development of predictive linear models of body composition, since it has an indicative capacity of the variables for estimation.
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Adiposidad , Antropometría/métodos , Estatura , Grosor de los Pliegues Cutáneos , Absorciometría de Fotón , Adolescente , Composición Corporal , Humanos , Modelos Lineales , Masculino , Modelos TeóricosRESUMEN
BACKGROUND: GATA2 is a transcription factor that is a critical regulator of gene expression in hematopoietic cells. GATA2 deficiency presents with multi-lineage cytopenia, mycobacterial, fungal and viral infections. Patients with GATA2 mutation have a high risk of developing myelodysplastic syndrome or acute myeloid leukemia. CASE PRESENTATION: We described a 43 years-old white male with 20-year follow-up of autoimmune and thrombotic phenomena, hypothyroidism, disseminated refractory Mycobacterium kansasii infection and MonoMAC syndrome. GATA2 c.1061 C > T; p.T354 M mutation was identified after he progressed from myelodysplastic pancytopenia to refractory anemia with excess blasts type II. His relatives were also investigated and he underwent unsuccessful haematopoietic stem cell transplantation. We discuss the clinical features, genetic diagnosis and treatment of this immunodeficiency disorder. CONCLUSIONS: This case illustrates the challenge how a multidisciplinary disease should be handle. Once usual causes of immunodeficiency were excluded, clinicians should considerGATA2 deficiency in patients with myelodysplasia and long-standing Mycobacterium kansasii infection.
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Deficiencia GATA2/genética , Factor de Transcripción GATA2/genética , Mutación , Infecciones por Mycobacterium no Tuberculosas/genética , Infecciones por Mycobacterium no Tuberculosas/microbiología , Mycobacterium kansasii/aislamiento & purificación , Síndromes Mielodisplásicos/genética , Adulto , Antibacterianos/uso terapéutico , Humanos , Masculino , Infecciones por Mycobacterium no Tuberculosas/complicaciones , Infecciones por Mycobacterium no Tuberculosas/tratamiento farmacológicoAsunto(s)
Deficiencia GATA2/genética , Factor de Transcripción GATA2/genética , Genes Recesivos/genética , Células Madre Hematopoyéticas/metabolismo , Adulto , Enfermedades Asintomáticas , Codón sin Sentido/genética , Deficiencia GATA2/sangre , Deficiencia GATA2/diagnóstico , Mutación de Línea Germinal , Células Madre Hematopoyéticas/patología , Heterocigoto , Humanos , Masculino , Persona de Mediana Edad , Linaje , Fenotipo , Polimorfismo de Nucleótido Simple , Adulto Joven , Dedos de Zinc/genéticaRESUMEN
The molecular basis of anhydrobiosis, the state of suspended animation entered by some species during extreme desiccation, is still poorly understood despite a number of transcriptome and proteome studies. We therefore conducted functional screening by RNA interference (RNAi) for genes involved in anhydrobiosis in the holo-anhydrobiotic nematode Panagrolaimus superbus. A new method of survival analysis, based on staining, and proof-of-principle RNAi experiments confirmed a role for genes involved in oxidative stress tolerance, while a novel medium-scale RNAi workflow identified a further 40 anhydrobiosis-associated genes, including several involved in proteostasis, DNA repair and signal transduction pathways. This suggests that multiple genes contribute to anhydrobiosis in P. superbus.
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Since the emergence of West Nile virus (WNV) in North America in 1999, there have been several reports of WNV activity in Central and South American countries. To detect WNV in Brazil, we performed a serological survey of horses from different regions of Brazil using recombinant peptides from domain III of WNV. Positive samples were validated with the neutralisation test. Our results showed that of 79 ELISA-positive horses, nine expressed WNV-specific neutralising antibodies. Eight of the infected horses were from the state of Mato Grosso do Sul and one was from the state of Paraíba. Our results provide additional evidence for the emergence of WNV in Brazil and for its circulation in multiple regions of the country.
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Anticuerpos Antivirales/sangre , Enfermedades de los Caballos/epidemiología , Fiebre del Nilo Occidental/veterinaria , Virus del Nilo Occidental/inmunología , Animales , Brasil/epidemiología , Ensayo de Inmunoadsorción Enzimática/veterinaria , Enfermedades de los Caballos/diagnóstico , Enfermedades de los Caballos/virología , Caballos , Pruebas de Neutralización , Estudios Seroepidemiológicos , Fiebre del Nilo Occidental/diagnóstico , Fiebre del Nilo Occidental/epidemiología , Virus del Nilo Occidental/aislamiento & purificaciónRESUMEN
The locus coeruleus (LC) plays a paradoxical role in chronic pain. Although largely known as a potent source of endogenous analgesia, increasing evidence suggests injury can transform the LC into a chronic pain generator. We sought to clarify the role of this system in pain. Here, we show optogenetic inhibition of LC activity is acutely antinociceptive. Following long-term spared nerve injury, the same LC inhibition is analgesic - further supporting its pain generator function. To identify inhibitory substrates that may naturally serve this function, we turned to endogenous LC mu opioid receptors (LC-MOR). These receptors provide powerful LC inhibition and exogenous activation of LC-MOR is antinociceptive. We therefore hypothesized that endogenous LC-MOR-mediated inhibition is critical to how the LC modulates pain. Using cell type-selective conditional knockout and rescue of LC-MOR receptor signaling, we show these receptors bidirectionally regulate thermal and mechanical hyperalgesia - providing a functional gate on the LC pain generator.
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ABSTRACT: Neuropathic pain causes both sensory and emotional maladaptation. Preclinical animal studies of neuropathic pain-induced negative affect could result in novel insights into the mechanisms of chronic pain. Modeling pain-induced negative affect, however, is variable across research groups and conditions. The same injury may or may not produce robust negative affective behavioral responses across different species, strains, and laboratories. Here, we sought to identify negative affective consequences of the spared nerve injury model on C57BL/6J male and female mice. We found no significant effect of spared nerve injury across a variety of approach-avoidance conflict, hedonic choice, and coping strategy assays. We hypothesized these inconsistencies may stem in part from the short test duration of these assays. To test this hypothesis, we used the homecage-based Feeding Experimentation Device version 3 to conduct 12-hour, overnight progressive ratio testing to determine whether mice with chronic spared nerve injury had decreased motivation to earn palatable food rewards. Our data demonstrate that despite equivalent task learning, spared nerve injury mice are less motivated to work for a sugar pellet than sham controls. Furthermore, when we normalized behavioral responses across all the behavioral assays we tested, we found that a combined normalized behavioral score is predictive of injury state and significantly correlates with mechanical thresholds. Together, these results suggest that homecage-based operant behaviors provide a useful platform for modeling nerve injury-induced negative affect and that valuable pain-related information can arise from agglomerative data analyses across behavioral assays-even when individual inferential statistics do not demonstrate significant mean differences.
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Telomere maintenance is essential for maintaining genome integrity in both normal and cancer cells. Without functional telomeres, chromosomes lose their protective structure and undergo fusion and breakage events that drive further genome instability, including cell arrest or death. One means by which this loss can be overcome in stem cells and cancer cells is via re-addition of G-rich telomeric repeats by the telomerase reverse transcriptase (TERT). During aging of somatic tissues, however, insufficient telomerase expression leads to a proliferative arrest called replicative senescence, which is triggered when telomeres reach a critically short threshold that induces a DNA damage response. Cancer cells express telomerase but do not entirely escape telomere instability as they often possess short telomeres; hence there is often selection for genetic alterations in the TERT promoter that result in increased telomerase expression. In this review, we discuss our current understanding of the consequences of telomere instability in cancer and aging, and outline the opportunities and challenges that lie ahead in exploiting the reliance of cells on telomere maintenance for preserving genome stability.
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Neoplasias , Telomerasa , Envejecimiento/genética , Senescencia Celular/genética , Inestabilidad Genómica , Humanos , Neoplasias/genética , Telomerasa/genética , Telomerasa/metabolismo , Telómero/genética , Telómero/metabolismoRESUMEN
OBJECTIVES: Absolute handgrip strength and adjusted by body mass index are useful to identify age-related conditions. However, these values are not accurate for older adults with extreme body size because of the nonlinear relationship between strength, height, and body mass. The purpose of this study was to determine cut-off points for age-related conditions of older adults using allometric coefficients to normalize grip strength by body size. DESIGN: Cross-sectional study. SETTING AND PARTICIPANTS: Data from 13,235 older adults of Study on Global Aging and Adult Health conducted in 6 low- and middle-income countries were analyzed. METHODS: Country- and sex-specific allometric exponents for body-size variables (mass and height) were computed with log-linear models. Partial correlation verified whether allometric normalization removed the effect of body size on grip strength. Cut-off points were established (<20th percentile) for low allometrically adjusted grip strength. RESULTS: Allometric exponents for normalization of grip strength were provided for body-size variables, ranging from 0.19 to 2.45. Allometric normalization removed the effect of body size on grip strength (r < 0.30). Overall, frequencies of low muscle strength were overestimated with international criteria (absolute grip strength) compared with the cut-off points proposed in this study. CONCLUSIONS AND IMPLICATIONS: The proposed allometric exponents normalized grip strength according to body-size variables. These exponents improved the accuracy in identifying age-related conditions in older adults with extreme body size. The variability between strength reveals the need for developing specific cut-off points for low- and middle-income countries. New cut-off points of low normalized grip strength with automatized applicability were proposed for health care providers use in clinical practice.
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Fuerza de la Mano , Fuerza Muscular , Anciano , Índice de Masa Corporal , Tamaño Corporal , Estudios Transversales , Femenino , Fuerza de la Mano/fisiología , Humanos , MasculinoRESUMEN
There has been an increasing interest in natural products with the ability to inhibit telomerase activity in tumour and cancerous cells. Green tea catechins have been reported previously to inhibit telomerase, but it was unknown whether catechins from other plant sources could exhibit this property. We isolated 2-(3,4-dihydroxyphenyl)-3,4-dihydro-2H-chromene-3,5,7-triol (catechin without the presence of a galloyl unit) from the stem bark of B. africana, and tested its ability to inhibit recombinant, partially purified telomerase produced in rabbit reticulocyte lysates. The B. africana catechin inhibited the telomere extension activity of telomerase with an IC50 of approximately 4.7 µg/ml. This finding indicates that the galloyl unit may not be solely responsible for the inhibition of telomerase activity by catechins. This is the first report of the telomerase-inhibiting potential of catechin from the stem bark of B. africana.
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Catequina , Fabaceae , Telomerasa , Animales , Catequina/farmacología , Fabaceae/química , Humanos , Corteza de la Planta/química , Conejos , Telomerasa/antagonistas & inhibidoresRESUMEN
PURPOSE: We compared laparoscopy assisted and open ileocystoplasty in an experimental model in pigs. We evaluated intraoperative aspects, postoperative recovery, peritoneal adhesions and functional results. MATERIALS AND METHODS: The study included 30 male pigs divided into 4 groups, including 10 with laparoscopy assisted ileocystoplasty, 10 with open surgery, 5 with sham laparoscopy and 5 with sham open surgery. Variables studied were total operative time, ileovesical anastomosis time, postoperative urodynamic findings (bladder capacity and compliance), daily and weekly weight gain, and intraperitoneal adhesions (incidence, type and score). RESULTS: Mean operative time in the laparoscopic and open groups was 179.4 and 69.6 minutes, respectively, which was significantly different (p <0.05). Mean ileovesical anastomosis time was also significantly different for laparoscopic vs open surgery (74.8 vs 31.8 minutes, p <0.05). Significant differences were observed in mean weekly weight gain during the first 4 weeks after surgery. Postoperatively bladder capacity and compliance differences among the groups were not significantly different (p >0.05). The overall incidence of intraperitoneal adhesions was not significantly different in all groups (p >0.05). However, in the open vs laparoscopy, sham laparoscopy and sham open surgery groups adhesion complexity was greater and mean score was higher (4.2 vs 2.8, 2.0 and 2.0, respectively), which was statistically significantly different (p <0.05). CONCLUSIONS: Laparoscopy assisted ileocystoplasty requires more operative time than open surgery. However, postoperative recovery is more rapid and intraperitoneal adhesions are less complex in pigs with laparoscopy assisted ileocystoplasty vs conventional surgery. Functional results are comparable for open and laparoscopy assisted ileocystoplasty.
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Íleon/cirugía , Laparoscopía , Vejiga Urinaria/cirugía , Animales , Masculino , Porcinos , Procedimientos Quirúrgicos Urológicos/métodosRESUMEN
The formation of scales in the petroleum industry, such as those composed of calcium and barium sulfates, may reduce productivity since these sediments can partially or totally obstruct the pipes. The mitigation of these inorganic precipitates can be accomplished by using scale inhibitors or by non-intrusive physical technologies. Here, we investigated the influence of magnetic field on the incrustations of barium sulfate by analyzing the concentration of barium and sulfate ions, the solution flow rate, the capillary tube geometry, and the magnetic field intensity in a homemade experimental unit supported on the monitoring of the dynamic differential pressure. The results show that the saline concentration and the flow rate of the solutions and the geometry of the capillary tube have a significant influence on the dynamics of barium sulfate incrustation. The presence of the magnetic field tends to prolong the induction time of the barium sulfate precipitation. A semi-empirical model was used to describe the effect of the studied variables on the barium sulfate incrustation behavior. The X-ray diffraction data of the precipitated particles analyzed using the Rietveld method suggest that the use of the magnetic field favor the formation of more crystalline particles and with smaller crystallite size than those formed in the absence of a magnetic field. Optical and scanning electron microscopy measurements also corroborate with these findings. The results from this study suggest that magnetic fields can be of interest in practical crystallization processes of barium sulfate and successfully applied to decrease the speed of barium sulfate incrustation in pipelines.
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BACKGROUND AND PURPOSE: Bladder dysfunction may lead to urinary incontinence and progressive kidney deterioration. When clinical treatment fails, bladder augmentation is the operation of choice in most cases. The purpose of this study was the standardization of the technique of videolaparoscopic ileocystoplasty in a porcine model and demonstration of a tutor-supervised learning curve. MATERIALS AND METHODS: The study was conducted on 15 Large-White male pigs (20-25 kg) that underwent ileocystoplasty with 15 cm of distal ileum shaped into a using extracorporeal technique and laparoscopic ileovesical anastomosis. Operative time, ileovesical anastomosis time, intraoperative complications, and extravasation after anastomosis were evaluated. To assess the learning curve, the animals were divided into three groups of five: group I (operated on in collaboration with a tutor), group II (treated under the supervision of tutor), and group III (without the tutor's collaboration or supervision). RESULTS: Total surgical time and ileovesical anastomosis time revealed significant differences (P < 0.05) between groups I and III (70% reduction) as well as between groups II and III (64% reduction). CONCLUSIONS: Laparoscopic ileocystoplasty in pigs is feasible without special laparoscopic material. Ten initial procedures with a tutor's help were important for technique acquisition and mastery. A sharp increase in efficiency occurs between the tenth and fifteenth procedures. These procedures should be executed at least ten times in the presence of the tutor to enable the surgeon to overcome the learning curve.
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Íleon/cirugía , Laparoscopía , Anastomosis Quirúrgica , Animales , Masculino , Instrumentos Quirúrgicos , Porcinos , Factores de Tiempo , Vejiga Urinaria/cirugíaRESUMEN
Thermoliquefaction of palm oil fiber was investigated using supercritical ethanol as solvent. A semi-continuous laboratory scale unit was developed to investigate the effects of temperature (300-500°C), heating rate (10-30°C.min-1) and cracking time (10-30min) on the conversion of biomass in bio-oil. The main advantage of the proposed process is that a pure solvent is pumping through the reactor that contains the biomass, dispensing the use of biomass slurries. The yield of bio-oil ranged from 56% to 84%, depending on the experimental conditions. It was observed that an increase in working temperature led to an increase in the bio-oil production. Cracking time and heating rate variation had not shown a considerable effect on the conversion of biomass. The chemical profiles of bio-oil determined by GC/MS, indicate that at low temperature mainly sugar derivatives are produced, while at higher temperatures alcohols and phenolic are the majority compounds of the bio-oil.
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Biotecnología/métodos , Fibras de la Dieta , Etanol/química , Aceites de Plantas/química , Temperatura , Biocombustibles/análisis , Biomasa , Elementos Químicos , Cromatografía de Gases y Espectrometría de Masas , Aceite de Palma , Solventes , TermogravimetríaAsunto(s)
Vacunas contra la COVID-19 , COVID-19 , Humanos , SARS-CoV-2 , Justicia Social , VacunaciónRESUMEN
O objetivo deste artigo foi verificar se os professores de Educação Física desenvolvem o tema "lutas" em suas aulas. Participaram do estudo oito professores de Educação Física de escolas públicas da microrregião oeste do estado do Paraná - Brasil. Foi utilizada uma entrevista semiestruturada e os dados foram tratados segundo a análise do conteúdo. Como resultados, verificamos que os professores desenvolvem o conteúdo "lutas" insuficientemente, utilizam apenas as atividades que dominam, são dependentes de materiais de apoio e, geralmente, ministram aulas teóricas ou realizam visitas com seus alunos às academias e trazem professores convidados. Concluímos que o tema "lutas" é pouco trabalhado em razão da formação inicial insuficiente, bem como necessita-se de uma formação continuada para essa abordagem (AU).
The objective was to verify if physical education teachers develop the theme "fights" in physical education classes. Eight Physical Education teachers from public schools in the western micro-region of the state of Paraná - Brazil participated in the study. A semi-structured interview was used, and the data were treated according to the content analysis. As a result, teachers develop the content " fights " insufficiently, developing only the activities they know, are dependent on support materials and teach theoretical classes or make visits with their students to the academies or bring in invited teachers. We conclude that the theme "fights" is little discussed, due to its insufficient initial training, as well as needing continued training for this thematization (AU).
El objetivo fue verificar si los profesores de educación física desarrollan el tema "luchas" en las clases de educación física. En el estudio participaron ocho profesores de Educación Física de escuelas públicas de la microrregión occidental del estado de Paraná - Brasil. Se utilizó una entrevista semiestructurada y los datos se trataron según el análisis de contenido. Como resultado, los docentes desarrollan los contenidos "luchas" de manera insuficiente, desarrollando solo las actividades que conocen, dependen de materiales de apoyo y generalmente imparten clases teóricas o realizan visitas con sus alumnos a las academias o traen profesores invitados. Concluimos que el tema "luchas" es poco discutido, por su insuficiente formación inicial, además de necesitar formación continua para esta tematización (AU).
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Humanos , Educación y Entrenamiento Físico , Instituciones Académicas , Artes Marciales , Maestros , Estudiantes , LuchaRESUMEN
The structure of the sward is important because it influences the responses of plants and animals in grazing conditions. The objective with this work was to evaluate the structural characteristics of the Marandu palisade grass pasture (Brachiaria brizantha syn. Urochloa brizantha) during spring and summer, depending on the condition of the sward at the end of winter. Four grazing conditions at the end of winter were evaluated: short (24.1 cm), short (25.2 cm)/mown (8 cm), tall (49.0 cm) and tall (50.0 cm)/mown (8 cm). The foliar area index was lower in the tall pasture than in the tall/mown pasture. The mass and the volumetric density of dead stem were higher in the tall pasture, intermediate in the short pasture, and lower in mowed pastures. At the beginning of the grazing period, the live stem mass was higher in the tall pasture. At the beginning and middle of the grazing period, the volumetric density of dead leaf lamina was lower in mowed pastures. At the beginning of the pasture period, the short pasture had a higher tiller number (TN). In the middle of the grazing period, the short and short/mown pastures had higher TN. At the end of the pasture period, the lowest TN value occurred in the tall pasture. The tall pasture at the end of winter presents an unfavorable structure to the animal in grazing, while the mowing and reduction in the height of the marandu palisade grass improves the structure of the sward in spring and summer.
A estrutura do pasto é importante porque influencia as respostas de plantas e animais em condições de pastejo. O objetivo com este trabalho foi avaliar as características estruturais do pasto de capim-marandu (Brachiaria brizantha syn. Urochloa brizantha) durante a primavera e o verão, em função da condição do pasto no fim do inverno. Quatro condições de pasto no fim do inverno foram avaliadas: baixo (24,1 cm), baixo (25,2 cm)/roçado (8 cm), alto (49,0 cm) e alto (50,0 cm)/roçado (8 cm). O índice de área foliar foi menor no pasto alto do que no pasto alto/roçado. A massa e a densidade volumétrica de colmo morto foram maiores no pasto alto, intermediárias no pasto baixo, e inferiores nos pastos roçados. No início do período de pastejo, a massa de colmo vivo foi maior no pasto alto. No início e meio do período de pastejo, a densidade volumétrica de lâmina foliar morta foi menor nos pastos roçados. No início do período de pastejo, o pasto baixo apresentou maior número de perfilho (NP). No meio do período de pastejo, os pastos baixo e baixo/roçado tiveram maior NP. No fim do período de pastejo, o menor valor de NP ocorreu no pasto alto. O pasto alto no fim do inverno apresenta estrutura desfavorável ao animal em pastejo, enquanto que a roçada e a redução da altura do capim-marandu melhora a estrutura do pasto na primavera e no verão.