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This study investigated muscle tissue in Bos indicus and crossbred bulls to explain differences in meat quality traits. Carcass traits, meat quality parameters, and biochemical and molecular investigations of myofibrillar proteins are described. Methods for evaluating pH, intramuscular fat (IMF), meat color (L*, a*, b*), water losses, tenderness, and molecular biology assays have been outlined. Specific procedures detailing calibration, sample preparation, and data analysis for each method are described. These include techniques such as infrared spectroscopy for IMF content, objective tenderness assessment, and electrophoretic separation of MyHC isoforms. Color parameters were highlighted as potential tools for predicting beef tenderness, a crucial quality trait influencing consumer decisions. The study employed the Warner-Bratzler shear force (WBSF) method, revealing values of 4.68 and 4.23 kg for Nellore and Angus-Nellore (P < 0.01), respectively. Total cooking losses and biochemical analyses, including myofibril fragmentation index (MFI), provided insights into tenderness variations. Muscle fiber types, particularly myosin heavy chain (MyHC) isoforms, were investigated, with a notable absence of MyHC-IIb isoform in the studied Zebu animals. The relationship between MyHC-I and meat tenderness revealed divergent findings in the literature, highlighting the complexity of this association. Overall, the study provides comprehensive insights into the factors influencing meat quality in Bos indicus and crossbred (Bos taurus × Bos indicus) bulls, offering valuable information for the beef industry.
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Músculo Esquelético , Animais , Bovinos , Masculino , Músculo Esquelético/química , Músculo Esquelético/metabolismo , Carne/análise , Carne Vermelha/análiseRESUMO
The use of effect biomarkers has contributed to the understanding of the sublethal effects of contaminants on different organisms. However, the analysis of genotoxic markers as an indicator of organism and environmental health in sharks is underexplored. Thus, the present study investigated the relationship between the genomic damage frequency in erythrocytes and metal(loid) concentrations in whole blood of three shark species (Galeocerdo cuvier, Negaprion brevirostris and Ginglymostoma cirratum), taking into account climatic seasonality. The results showed that G. cuvier, an apex predator, presented the highest total erythrocyte genomic damage frequencies together with the highest mean whole blood concentrations of Al, Cd, Cr, Fe, Mn, Ni, Pb and Zn. The shark N. brevirostris also presented high levels of metal(loid), indicating a greater susceptibility to these contaminants in species that preferentially feed on fish. In contrast, G. cirratum, a mesopredator, presented the lowest erythrocyte damage frequencies and whole blood metal(loid) concentrations. The presence of micronuclei was the most responsive biomarker, and Al, As and Zn had an important effect on the genomic damage frequencies for all species evaluated. Zn concentration influenced the binucleated cells frequencies and Al concentration had an effect on the total damage and micronuclei frequencies in G. cuvier and N. brevirostris. Binucleated cells and blebbed nuclei frequencies were affected by As concentration, especially in G. cirratum, while showing a strong and positive correlation with most of the metals analyzed. Nonetheless, baseline levels of metal(loid) blood concentrations and erythrocyte genomic damage frequencies in sharks have not yet been established. Therefore, minimum risk levels of blood contaminants concentrations on the health of these animals have also not been determined. However, the high genomic instability observed in sharks is of concern considering the current health status of these animals, as well as the quality of the environment studied.
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This meta-analysis aims to investigate the effects of residual feed intake (RFI) phenotype on performance, nutrient utilization and meat quality traits in Zebu (Bos indicus) cattle. Twenty-three peer-reviewed publications with 37 treatment means were included in the dataset. Weighted mean difference analysis compared animals categorized into low RFI (more efficient) versus medium or high RFI (less efficient) groups. Data heterogeneity via meta-regression and subgroup analysis, considering variables such as animal age, sex class, experimental duration, RFI group, dietary concentrate, and estimated metabolizable energy intake were also explored. The predominant genetic group of cattle in the dataset was Nellore (89.18%), followed by Brahman (10.81%). More efficient animals (low RFI phenotype) exhibited less dry matter intake (DMI; P < 0.010) than medium or high RFI animals (-0.95 kg vs. -0.42 kg/d). Cattle dietary crude protein and fiber digestibility were consistent across RFI groups (P > 0.05), while dietary ether extract digestibility tended to decrease (P = 0.050) in low RFI animals (-13.20 g/kg DM). Low RFI animals tended to increased (P = 0.065) ribeye area (REA) compared to the high/medium RFI groups, while carcass backfat thickness (BFT) decreased (P = 0.042) compared to high/medium RFI groups. Moreover, there was an increase (P < 0.001) of 0.22 kg in Warner-Bratzler shear force (WBSF) and a reduction (P < 0.001) in the myofibrillar fragmentation index (MFI) in low RFI animals. Meat color parameters (lightness [L*] and yellowness [b*]) and visual marbling scores were consistent (P > 0.05) across RFI groups. In conclusion, Zebu cattle classified as efficient (low RFI) exhibited reduced DMI, which improves their feed efficiency. However, BFT and meat quality parameters such as tenderness (WBSF and MFI) and redness [a*] were compromised by low RFI phenotype, highlighting the challenge of enhancing feed efficiency and meat quality traits in Zebu cattle.
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Ração Animal , Fenômenos Fisiológicos da Nutrição Animal , Dieta , Animais , Bovinos/fisiologia , Feminino , Masculino , Ração Animal/análise , Dieta/veterinária , Fenótipo , Carne Vermelha/análiseRESUMO
Artificial intelligence is poised to rapidly reshape many fields, including that of skin cancer screening and diagnosis, both as a disruptive and assistive technology. Together with the collection and availability of large medical data sets, artificial intelligence will become a powerful tool that can be leveraged by physicians in their diagnoses and treatment plans for patients. This comprehensive review focuses on current progress toward AI applications for patients, primary care providers, dermatologists, and dermatopathologists, explores the diverse applications of image and molecular processing for skin cancer, and highlights AI's potential for patient self-screening and improving diagnostic accuracy for non-dermatologists. We additionally delve into the challenges and barriers to clinical implementation, paths forward for implementation and areas of active research.
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The asymptomatic and slow progressive nature of cardiopathies represents a risk to the welfare of avian species in human care. Diagnosis and treatment of cardiac disease in birds pose a challenge due to unique anatomic and physiologic characteristics. Comprehensive cardiac assessments with diagnostic tools such as echocardiography, color-Doppler, the biomarker cardiac troponin I (cTn1), and cholesterol serum concentrations have been utilized in different bird species with varying success. Saddle-billed storks (Ephippiorhynchus senegalensis) have been maintained in human care for over 80 yrs and several institutions have noted heart murmurs and cardiomegaly. Despite these findings, peer-reviewed literature describing cardiopathies is lacking for this species. This case series documents the identification of mitral valve regurgitation in saddle-billed storks in a breeding center. Transcoelomic echocardiography using a ventromedial approach with a two-chambered view and color Doppler was utilized. Echocardiographic measurements were taken and compared 1 yr later in most of the birds. There was left atrial enlargement and worsened mitral regurgitation in one geriatric patient, and no progression of the disease in two young birds. Serum samples showed that cTn1 had different concentrations depending on the severity of the disease, whereas cholesterol was within reference range for all birds. Treatment with digoxin and pimobendan was recommended in one bird, serum concentrations of digoxin were tested in a 6-mon span, results were within therapeutic range, and there were no overt adverse effects. There was a suspected genetic component in this population, as four of the five birds with confirmed mitral regurgitation were related.
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Insuficiência da Valva Mitral , Animais , Humanos , Insuficiência da Valva Mitral/diagnóstico , Insuficiência da Valva Mitral/veterinária , Aves , Ecocardiografia/veterinária , Digoxina , ColesterolRESUMO
OBJECTIVE: To assess intraocular pressure (IOP) development in cranes and determine the impact of age, weight, species, head position, and sex. ANIMALS STUDIED: Whooping cranes (WC) (Grus americana), and Mississippi-sandhill cranes (MSC) (Grus canadensis pulla). PROCEDURES: Chicks were manually restrained on days 1-3, 7, 21, 35, 60, 75, and 120 for routine examinations. IOP was opportunistically measured utilizing the Tonovet Plus® in D setting with the head above the heart (AH) and below the heart (BH). Values were also obtained longitudinally in adults (>120 days old) upon presentation in 1 year. RESULTS: Intraocular pressure was highly correlated with age and weight in chicks. For every kilogram gained, IOP increased 2.46 ± 0.08 mmHg in WC and 2.66 ± 0.11 mmHg in MSC. Once hatched, IOP increased 1.13 ± 0.04 mmHg in WC and 0.87 ± 0.04 mmHg in MSC every 10 days. IOP was similar to adults at 120 days of age. In adult WC, mean IOP AH was 24.0 ± 0.4 mmHg, and BH was 27.9 ± 0.4 mmHg, there was a significant difference regarding head positioning and sex, females (25.3 ± 0.4 mm Hg) had lower IOP than males (26.5 ± 0.4 mmHg). In adult MSC, mean IOP AH was 20.7 ± 0.4 mmHg, and BH was 24.6 ± 0.4 mmHg. The difference between head positioning was significant. CONCLUSIONS: This study documents the correlation between IOP and weight or age during early development in cranes, as well as the importance of head positioning.
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Ryanodine receptors (RyR) are intracellular Ca2+ channels localized in the endoplasmic reticulum, where they act as critical mediators of Ca2+-induced Ca2+ calcium release (CICR). In the brain, mammals express in both neurons, and non-neuronal cells, a combination of the three RyR-isoforms (RyR1-3). Pharmacological approaches, which do not distinguish between isoforms, have indicated that RyR-isoforms contribute to brain function. However, isoform-specific manipulations have revealed that RyR-isoforms display different subcellular localizations and are differentially associated with neuronal function. These findings raise the need to understand RyR-isoform specific transcriptional regulation, as this knowledge will help to elucidate the causes of neuronal dysfunction for a growing list of brain disorders that show altered RyR channel expression and function.
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Retículo Endoplasmático , Canal de Liberação de Cálcio do Receptor de Rianodina , Animais , Canal de Liberação de Cálcio do Receptor de Rianodina/genética , Canal de Liberação de Cálcio do Receptor de Rianodina/metabolismo , Retículo Endoplasmático/metabolismo , Regulação da Expressão Gênica , Encéfalo/metabolismo , Cálcio/metabolismo , Isoformas de Proteínas/metabolismo , Rianodina/metabolismo , Mamíferos/metabolismoRESUMO
The objective was to evaluate the supplementation strategy's effect on beef cattle during the growing phase and two systems during the finishing phase. One hundred and twenty young bulls were randomly divided in a 2 × 2 factorial design to receive either mineral (ad libitum) or protein + energy (3 g/kg body weight (BW)/day) during the growing phase and pasture plus concentrate supplementation (20 g/kg BW/day) or feedlot (25:75% corn silage:concentrate) during the finishing phase. Feedlot-fed bulls had meat (Longissimus thoracis-LT) with a higher content of lipids and saturated and monounsaturated fatty acids and a greater upregulation of stearoyl-CoA desaturase and sterol regulatory element-binding protein-1c than animals that fed on pasture (p < 0.05). On the other hand, pasture-fed bulls had meat with a higher content of α-linoleic acid, linolenic acid, and n6 and a greater n6:n3 ratio compared to the feedlot-fed group (p < 0.05). In addition, meat from pasture-fed bulls during the finishing phase had 17.6% more isocitrate dehydrogenase enzyme concentration than the feedlot group (p = 0.02). Mineral-fed and pasture-finished bulls showed down-regulation of peroxisome proliferator-activated receptor gamma (p < 0.05), while the bulls fed protein + energy and finished in the feedlot had higher carnitine palmitoyltransferase 2 expression (p ≤ 0.013). In conclusion, mineral or protein + energy supplementation in the growing does not affect the fatty acid composition of intramuscular fat of LT muscle. In the finishing phase, feeding bulls in the feedlot upregulates the lipogenic genes and consequently improves the intramuscular fat content in the meat.
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Enteric methane emission is the main source of greenhouse gas contribution from dairy cattle. Therefore, it is essential to evaluate drivers and develop more accurate predictive models for such emissions. In this study, we built a large and intercontinental experimental dataset to: (1) explain the effect of enteric methane emission yield (g methane/kg diet intake) and feed conversion (kg diet intake/kg milk yield) on enteric methane emission intensity (g methane/kg milk yield); (2) develop six models for predicting enteric methane emissions (g/cow/day) using animal, diet, and dry matter intake as inputs; and to (3) compare these 6 models with 43 models from the literature. Feed conversion contributed more to enteric methane emission (EME) intensity than EME yield. Increasing the milk yield reduced EME intensity, due more to feed conversion enhancement rather than EME yield. Our models predicted methane emissions better than most external models, with the exception of only two other models which had similar adequacy. Improved productivity of dairy cows reduces emission intensity by enhancing feed conversion. Improvement in feed conversion should be prioritized for reducing methane emissions in dairy cattle systems.
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This study aimed to evaluate by wide-expression profile analysis how early weaning at 120 days can alter the skeletal muscle metabolism of calves supplemented with a concentrated diet until the growth phase. Longissimus thoracis muscle samples were obtained by biopsy from two groups of calves, early weaned (EW; n = 8) and conventionally weaned (CW; n = 8) at two different times (120 days of age-T1 [EW] and 205 days of age-T2 [CW]). Next, differential gene expression analysis and functional enrichment of metabolic pathways and biological processes were performed. The results showed respectively 658 and 165 differentially expressed genes when T1 and T2 were contrasted in the early weaning group and when early and conventionally weaned groups were compared at T2. The FABP4, SCD1, FASN, LDLR, ADIPOQ, ACACA, PPARD, and ACOX3 genes were prospected in both comparisons described above. Given the key role of these differentially expressed genes in lipid and fatty acid metabolism, the results demonstrate the effect of diet on the modulation of energy metabolism, particularly favoring postnatal adipogenesis and lipogenesis, as well as a consequent trend in obtaining better quality cuts, as long as an environment for the maintenance of these alterations until adulthood is provided.
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Anthropogenically induced global climate change has caused profound impacts in the world ocean. Climate change related stressors, like ocean acidification (OA) and warming (OW) can affect physiological performance of marine species. However, studies evaluating the impacts of these stressors on algae-herbivore interactions have been much more scarce. We approached this issue by assessing the combined impacts of OA and OW on the physiological energetics of the herbivorous snail Tegula atra, and whether this snail is affected indirectly by changes in biochemical composition of the kelp Lessonia spicata, in response to OA and OW. Our results show that OA and OW induce changes in kelp biochemical composition and palatability (organic matter, phenolic content), which in turn affect snails' feeding behaviour and energy balance. Nutritional quality of food plays a key role on grazers' physiological energetics and can define the stability of trophic interactions in rapidly changing environments such as intertidal communities.
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Kelp , Água do Mar , Animais , Água do Mar/química , Herbivoria/fisiologia , Concentração de Íons de Hidrogênio , Acidificação dos Oceanos , Ecossistema , Mudança Climática , Caramujos , Oceanos e Mares , Aquecimento GlobalRESUMO
Bacteria can communicate through quorum sensing, allowing them to develop different survival or virulence traits that lead to increased bacterial resistance against conventional antibiotic therapy. Here, fifteen essential oils (EOs) were investigated for their antimicrobial and anti-quorum-sensing activities using Chromobacterium violaceum CV026 as a model. All EOs were isolated from plant material via hydrodistillation and analyzed using GC/MS. In vitro antimicrobial activity was determined using the microdilution technique. Subinhibitory concentrations were used to determine anti-quorum-sensing activity by inhibition of violacein production. Finally, a possible mechanism of action for most bioactive EOs was determined using a metabolomic approach. Among the EOs evaluated, the EO from Lippia origanoides exhibited antimicrobial and anti-quorum activities at 0.37 and 0.15 mg/mL, respectively. Based on the experimental results, the antibiofilm activity of EO can be attributed to the blockage of tryptophan metabolism in the metabolic pathway of violacein synthesis. The metabolomic analyses made it possible to see effects mainly at the levels of tryptophan metabolism, nucleotide biosynthesis, arginine metabolism and vitamin biosynthesis. This allows us to highlight the EO of L. origanoides as a promising candidate for further studies in the design of antimicrobial compounds against bacterial resistance.
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The objective of this study was to evaluate different methods of predicting body weight (BW) and hot carcass weight (HCW) from biometric measurements obtained through three-dimensional images of Nellore cattle. We collected BW and HCW of 1350 male Nellore cattle (bulls and steers) from four different experiments. Three-dimensional images of each animal were obtained using the Kinect® model 1473 sensor (Microsoft Corporation, Redmond, WA, USA). Models were compared based on root mean square error estimation and concordance correlation coefficient. The predictive quality of the approaches used multiple linear regression (MLR); least absolute shrinkage and selection operator (LASSO); partial least square (PLS), and artificial neutral network (ANN) and was affected not only by the conditions (set) but also by the objective (BW vs. HCW). The most stable for BW was the ANN (Set 1: RMSEP = 19.68; CCC = 0.73; Set 2: RMSEP = 27.22; CCC = 0.66; Set 3: RMSEP = 27.23; CCC = 0.70; Set 4: RMSEP = 33.74; CCC = 0.74), which showed predictive quality regardless of the set analyzed. However, when evaluating predictive quality for HCW, the models obtained by LASSO and PLS showed greater quality over the different sets. Overall, the use of three-dimensional images was able to predict BW and HCW in Nellore cattle.
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Molasses must be one of the most used foods in the diet of ruminant animals; however, there is no consensus on the effect of including molasses on carcass parameters. In this context, the objective was to evaluate the effect of including molasses in the diet of feedlot cattle on performance and carcass parameters. Thirteen peer-reviewed publications with 45 treatment means were included in the dataset. The effect of molasses in beef cattle diets was evaluated by examining the weighted mean differences (WMD) between molasses treatment (diet with molasses) and control diet (diet without molasses). Heterogeneity was explored by meta-regression and subgroup analysis using genetic type and experimental period, molasses in diet (g/kg dry matter (DM)), molasses type, concentrate in diet (g/kg DM), and forage type. The inclusion of molasses in the diet increased dry matter digestibility, but reduced NDF digestibility, carcass weight, subcutaneous, and visceral fat. The main sources of variation for the responses with molasses inclusion on intake, digestibility, performance, and carcass parameters were the level of molasses inclusion and the experimental period. In general context, the inclusion of molasses in the diet between 100 to 150 g/kg of DM did not affect performance and carcass parameters. However, the inclusion of molasses above 200 g/kg reduces the average daily gain and carcass weight.
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Ração Animal , Zea mays , Bovinos , Animais , Ração Animal/análise , Melaço , Digestão , Dieta/veterinária , Suplementos NutricionaisRESUMO
Elasmobranchs can bioaccumulate and biomagnify pollutants. However, few studies are directed to the effects of pollutants on the health of these animals, and in most cases, are limited to the analysis of biochemical markers. Thus, the incidence of genomic damage among shark species inhabiting a protected ocean island in the South Atlantic was investigated in association with the analysis of pollutants in seawater sample. High levels of genomic damage were identified, especially in Negaprion brevirostris and Galeocerdo cuvier, in addition to interspecific variations that may be related to characteristics such as animal size, metabolism and habits. High concentrations of Surfactants were observed in seawater sample, in addition to low concentrations of Cadmium, Lead, Copper, Chromium, Zinc, Manganese, and Mercury. The results evidenced the potential of shark species as a bioindicator of environmental quality and allowed assessing the anthropic impact on the archipelago, which currently drives its economy through tourism.
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Poluentes Ambientais , Mercúrio , Tubarões , Animais , Humanos , Tubarões/metabolismo , Mercúrio/metabolismo , Biomarcadores Ambientais , Genômica , Poluentes Ambientais/metabolismoRESUMO
Most Candida species are opportunistic pathogens with the ability to form biofilms, which increases their resistance to antifungal drug therapies and the host immune response. Essential oils (EOs) are an alternative for developing new antimicrobial drugs, due to their broad effect on cellular viability, cell communication, and metabolism. In this work, we evaluated the antifungal and antibiofilm potential of fifty EOs on C. albicans ATCC 10231, C. parapsilosis ATCC 22019, and Candida auris CDC B11903. The EOs' antifungal activity was measured by means of a broth microdilution technique to determine the minimum inhibitory and fungicidal concentrations (MICs/MFCs) against the different Candida spp. strains. The effects on biofilm formation were determined by a crystal violet assay using 96-well round-bottom microplates incubated for 48 h at 35 °C. The EOs from Lippia alba (Verbenaceae family) carvone-limonene chemotype and L. origanoides exhibited the highest antifungal activity against C. auris. The L. origanoides EOs also presented antifungal and antibiofilm activity against all three Candida spp., thus representing a promising alternative for developing new antifungal products focused on yeast infections, especially those related to biofilm formation, virulence factors, and antimicrobial resistance.
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The present work aimed to study, predict and understand benzene migration that occurred during an industrial spill using numerical simulation by computational fluid dynamics. Advection, diffusion and adsorption were the main mechanisms considered that governed the spill incident. The incident occurred due to a fracture under a fuel oil storage tank. The tank was located on a hill 18 m high, and the initial value of benzene concentration (soil saturation) was 60 ppm. When the spill was discovered, samples in the affected zone were taken using an experimental design. Many samples showed a greater concentration of benzene than allowed by Mexican Official Standards (MOSs) (15 ppm). The concentrations found 100 m away from the spill were around 60 to 15 ppm. Due to the spill being under the tank, it was difficult to discover. The numerical simulation provided an estimate that the spill started around 2 years ago. The type of soil in the afflicted zone is rocky, and, consequently, it is difficult to estimate how long it will take to reach the concentration allowed by the MOSs, but the numerical simulation predicts that this concentration will be reached in 14 years. Experimental values of the spill contaminant concentration were statistically similar to the CFD estimated data (p < 0.05).
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Óleos Combustíveis , Poluição por Petróleo , Benzeno/análise , Hidrodinâmica , Hidrocarbonetos , Simulação por Computador , Poluição por Petróleo/análiseRESUMO
Resumen Objetivo: Realizar un análisis descriptivo de los incidentes en oftalmología reportados por médicos oftalmólogos de Argentina. Métodos: Se realizó un estudio basado en una encuesta desarrollada mediante un sistema electrónico, en agosto de 2021, dirigido a médicos oftalmólogos de Argentina. Se solicitó la descripción de incidentes oftalmológicos, clasificándolos en cuatro grupos, acorde a lo descrito por Organización Mundial de la Salud, en A: "Incidentes, casi-accidentes (no alcanzaron a los pacientes)"; B: "Incidentes (que alcanzaron al paciente, pero sin daño)"; C: "Incidentes prevenibles con daño" y D: "Incidentes no prevenibles con daño". El instructivo de la encuesta explicó la terminología y ofreció ejemplos de cada tipo de incidentes, que fueron evaluados mediante un proceso estadístico descriptivo. Resultados: Participaron 264 médicos oftalmólo gos quienes informaron 434 incidentes. A- Incidentes sin alcance al paciente: 125 casos (28.8%). B- Incidentes que alcanzaron al paciente sin daño: 117 casos. (27%). C- Incidentes prevenibles, con daño: 96 casos (22.1%). D- Incidentes no prevenibles con daño: 96 casos (22.1%). Los incidentes vinculados al uso de gotas fueron los más frecuentes en los 4 grupos (68, 75, 13 y 29 incidentes respectivamente). Conclusión: El 77.9% de los incidentes comunicados en este estudio se podrían haber evitado con adecuadas medidas de seguridad, siendo los más frecuentes los asociados a la utilización de gotas oftálmicas.
Abstract Objective: To perform a descriptive analysis of incidents in ophthalmology reported by ophthal mologists of Argentina. Methods: A questionnaire-based study was performed by an electronic survey during August 2021, including ophthalmologists of Argentina, requesting the description of ophthalmological incidents, which were classified in four groups, in accordance with World Health Organization Definition, as follow: A- "Inci dents, almost-accidents (patient no affected)"; B: "Incidents (patient affected without damage)"; C: "Preventable incidents, with damage", and D: "Not Preventable incidents, with damage". An instructive was supported in the survey explaining these definitions with examples of each kind of incidents. Data was processed for descriptive statistics. Results: The survey was performed by 264 ophthalmologists, reporting 434 incidents: A- Incidents, almost-accidents (patient not affected): 125 cases (28.8%). B- Incidents (patient affected without damage): 117 cases (27%). C- Preventable incidents, with damage: 96 cases (22.1%). D- "Not Preventable incidents, with damage: 96 cases (22.1%). In four groups the most frequent incidents were those associated with the use of ophthalmic drops (68, 75, 13, and 29 incidents respectively). Conclusion: Most of the incidents (77.9%) reported in this study could be avoided if appropriate safety measures were taken. Ophthalmic drops related incidents were the most frequent.
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This study investigated the skeletal muscle proteome of crossbred bulls and steers with the aim of explaining the differences in carcass and meat quality traits. Therefore, 640 post-weaning Angus-Nellore calves were fed a high-energy diet for a period of 180 days. In the feedlot trial, comparisons of steers (n = 320) and bulls (n = 320) showed lower (P < 0.01) average daily gain (1.38 vs. 1.60 ± 0.05 kg/d), final body weight (547.4 vs. 585.1 ± 9.3 kg), which resulted in lower hot carcass weight (298.4 vs. 333.7 ± 7.7 kg) and ribeye area (68.6 vs. 81.0 ± 2.56 cm2). Steers had higher (P < 0.01) carcass fatness, meat color parameters (L*, a*, b*, chroma (C*), hue (h°)) and lower ultimate pH. Moreover, lower (P < 0.01) Warner-Bratzler shear force (WBSF) were observed in steers compared to bulls (WBSF = 3.68 vs. 4.97 ± 0.08 kg; and 3.19 vs. 4.08 ± 0.08 kg). The proteomic approach using two-dimensional electrophoresis, mass spectrometry and bioinformatics procedures revealed several differentially expressed proteins between steers and bulls (P < 0.05). Interconnected pathways and substantial changes were revealed in biological processes, molecular functions, and cellular components between the post-mortem muscle proteomes of the compared animals. Steers had increased (P < 0.05) abundance of proteins related to energy metabolism (CKM, ALDOA, and GAPDH), and bulls had greater abundance of proteins associated with catabolic (glycolysis) processes (PGM1); oxidative stress (HSP60, HSPA8 and GSTP1); and muscle structure and contraction (TNNI2 and TNNT3). The better carcass (fatness and marbling degree) and meat quality traits (tenderness and color parameters) of steers were associated with higher abundance of key proteins of energy metabolism and lower abundance of enzymes related to catabolic processes, oxidative stress, and proteins of muscle contraction SIGNIFICANCE: Sexual condition of cattle is known to be an important factor affecting animal performances and growth as well as the carcass and meat quality traits. The investigation of skeletal muscle proteome help a better understanding of the origin of the differences in quality traits between bulls and steers. The inferior meat quality of bulls was found to be due to the greater expression of proteins associated with primary and catabolic processes, oxidative stress, and muscle contraction. Steers had greater expression of proteins, from which several are known biomarkers of beef quality (mainly tenderness).