Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 16 de 16
Filtrar
Más filtros










Intervalo de año de publicación
1.
Medicine (Baltimore) ; 103(25): e38623, 2024 Jun 21.
Artículo en Inglés | MEDLINE | ID: mdl-38905403

RESUMEN

The incidence of papillary thyroid carcinoma (PTC) has increased significantly in recent years, and for patients with metastatic and recurrent PTC, the options for treatment currently available are insufficient. To date, the exact molecular mechanism underlying PTC is still not fully understood. 5-Methylcytosine (m5C) RNA methylation is associated with the prognosis of a variety of tumors. However, the molecular mechanisms and biomarkers associated with m5C in the diagnosis, treatment, and prognosis of this disease have not been fully elucidated. Ten m5C regulators with significantly different expression levels were included in this study. Immune infiltration analysis revealed significant negative correlations between most of these regulators and regulatory T cells. TRDMT1, NSUN5, and NSUN6 had high weights and strong correlations in the protein-protein interaction network. Using gene ontology, Kyoto Encyclopedia of Genes and Genomes, and gene set enrichment analysis, 1489 differentially expressed genes were screened from The Cancer Genome Atlas messenger RNA matrix, indicating that these differentially expressed genes were significantly enriched in various pathways and functions related to cancers. Four m5C regulators, NSUN2, NSUN4, NSUN6, and DNMT3B, were screened as prognostic markers by least absolute shrinkage and selection operator regression analysis, and NSUN2 and NSUN6 were identified as risk factors for poor prognosis. We found that the prognostic prediction model constructed using the m5C regulators NSUN2, NSUN4, NSUN6, and DNMT3B showed good prognostic prediction ability and diagnostic ability. This model was applied to predict the survival probability of patients with PTC, the prediction ability of 5-year survival was the best. The multi-factor prognostic prediction model combined with the tumor node metastasis stage and risk score grouping showed better prognostic predictive power.


Asunto(s)
Biomarcadores de Tumor , Cáncer Papilar Tiroideo , Neoplasias de la Tiroides , Humanos , Cáncer Papilar Tiroideo/genética , Cáncer Papilar Tiroideo/mortalidad , Cáncer Papilar Tiroideo/patología , Pronóstico , Neoplasias de la Tiroides/genética , Neoplasias de la Tiroides/mortalidad , Neoplasias de la Tiroides/patología , Biomarcadores de Tumor/genética , 5-Metilcitosina/análogos & derivados , 5-Metilcitosina/metabolismo , Masculino , Femenino , Regulación Neoplásica de la Expresión Génica , Metilación , Persona de Mediana Edad
2.
Hum Cell ; 37(4): 1156-1169, 2024 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-38814517

RESUMEN

To explore the effects of ß-Sitosterol upon hepatocellular carcinoma cell proliferation, apoptosis, migration, invasion, and epithelial-mesenchymal transition (EMT), and to investigate the underlying mechanism using network pharmacology. Human hepatocellular carcinoma cell lines (Huh-7 and HCCLM3) were expose to gradient concentrations of ß-Sitosterol (5 µg/mL, 10 µg/mL, and 20 µg/mL). Cell viability and proliferation were assessed using MTT, CCK-8, colony formation, and EdU assays.Flow cytometry was employed to evaluate cell cycle and apoptosis. Scratch and Transwell assays were performed, respectively, to detect cell migration and invasion. The levels of apoptosis-associated proteins (BAX, BCL2, and cleaved caspase3) as well as EMT-associated proteins (E-cadherin, N-cadherin, Snail, and Vimentin) were detected in Huh-7 and HCCLM3 cell lines using Western blot analysis. The drug target gene for ß-Sitosterol was screened via PubChem and subsequently evaluated for expression in the GSE112790 dataset. In addition, the expression level of glycogen synthase kinase 3 beta (GSK3B) within the Cancer Genome Atlas-Liver Hepatocellular Carcinoma (TCGA-LIHC) database was analyzed, along with its correlation to the survival outcomes of patients with hepatocellular carcinoma. The diagnostic efficiency of GSK3B was assessed by analyzing the ROC curve. Subsequently, Huh-7 and HCCLM3 cell lines were transfected with the overexpression vector of GSK3B and then treated with ß-Sitosterol to further validate the association between GSK3B and ß-Sitosterol. GSK3B demonstrated a significantly elevated expression in patients with hepatocellular carcinoma, which could predict hepatocellular carcinoma patients' impaired prognosis based on GEO dataset and TCGA database. GSK3B inhibitor (CHIR-98014) notably inhibited cell proliferation and invasion, promoted cell apoptosis and cell cycle arrest at G0/G1 phase in hepatocellular carcinoma cells. ß-Sitosterol treatment further promoted the efffects of GSK3B inhibitor on hepatocellular carcinoma cells. GSK3B overexpression has been found to enhance the proliferative and invasive capabilities of hepatocellular carcinoma cells. Furthermore it has been observed that GSK3B overexpression, it has been obsear can partially reverse the inhibitory effect of ß-Sitosterol upon hepatocellular. ß-Sitosterol suppressed hepatocellular carcinoma cell proliferation and invasion, and enhanced apoptosis via inhibiting GSK3B expression.


Asunto(s)
Apoptosis , Carcinoma Hepatocelular , Proliferación Celular , Transición Epitelial-Mesenquimal , Glucógeno Sintasa Quinasa 3 beta , Neoplasias Hepáticas , Sitoesteroles , Humanos , Sitoesteroles/farmacología , Glucógeno Sintasa Quinasa 3 beta/metabolismo , Glucógeno Sintasa Quinasa 3 beta/genética , Carcinoma Hepatocelular/patología , Carcinoma Hepatocelular/genética , Carcinoma Hepatocelular/tratamiento farmacológico , Carcinoma Hepatocelular/metabolismo , Neoplasias Hepáticas/patología , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/tratamiento farmacológico , Neoplasias Hepáticas/metabolismo , Proliferación Celular/efectos de los fármacos , Proliferación Celular/genética , Apoptosis/efectos de los fármacos , Apoptosis/genética , Línea Celular Tumoral , Transición Epitelial-Mesenquimal/efectos de los fármacos , Transición Epitelial-Mesenquimal/genética , Movimiento Celular/efectos de los fármacos , Movimiento Celular/genética , Expresión Génica/genética , Expresión Génica/efectos de los fármacos , Fenotipo , Invasividad Neoplásica/genética , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/genética , Farmacología en Red , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos
3.
Environ Res ; 251(Pt 2): 118670, 2024 Jun 15.
Artículo en Inglés | MEDLINE | ID: mdl-38493849

RESUMEN

The surfactant-enhanced bioremediation (SEBR) of organic-contaminated soil is a promising soil remediation technology, in which surfactants not only mobilize pollutants, but also alter the mobility of bacteria. However, the bacterial response and underlying mechanisms remain unclear. In this study, the effects and mechanisms of action of a selected nonionic surfactant (Tween 80) on Pseudomonas aeruginosa transport in soil and quartz sand were investigated. The results showed that bacterial migration in both quartz sand and soil was significantly enhanced with increasing Tween 80 concentration, and the greatest migration occurred at a critical micelle concentration (CMC) of 4 for quartz sand and 30 for soil, with increases of 185.2% and 27.3%, respectively. The experimental results and theoretical analysis indicated that Tween 80-facilitated bacterial migration could be mainly attributed to competition for soil/sand surface sorption sites between Tween 80 and bacteria. The prior sorption of Tween 80 onto sand/soil could diminish the available sorption sites for P. aeruginosa, resulting in significant decreases in deposition parameters (70.8% and 33.3% decrease in KD in sand and soil systems, respectively), thereby increasing bacterial transport. In the bacterial post-sorption scenario, the subsequent injection of Tween 80 washed out 69.8% of the bacteria retained in the quartz sand owing to the competition of Tween 80 with pre-sorbed bacteria, as compared with almost no bacteria being eluted by NaCl solution. Several machine learning models have been employed to predict Tween 80-faciliated bacterial transport. The results showed that back-propagation neural network (BPNN)-based machine learning could predict the transport of P. aeruginosa through quartz sand with Tween 80 in-sample (2 CMC) and out-of-sample (10 CMC) with errors of 0.79% and 3.77%, respectively. This study sheds light on the full understanding of SEBR from the viewpoint of degrader facilitation.


Asunto(s)
Biodegradación Ambiental , Aprendizaje Automático , Polisorbatos , Pseudomonas aeruginosa , Tensoactivos , Polisorbatos/química , Tensoactivos/química , Pseudomonas aeruginosa/efectos de los fármacos , Microbiología del Suelo , Porosidad , Contaminantes del Suelo/química
4.
IEEE Trans Image Process ; 33: 957-971, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38252569

RESUMEN

Clustering is a fundamental and important step in many image processing tasks, such as face recognition and image segmentation. The performance of clustering can be largely enhanced if relevant weak supervision information is appropriately exploited. To achieve this goal, in this paper, we propose the Compound Weakly Supervised Clustering (CSWC) method. Concretely, CSWC incorporates two types of widely available and easily accessed weak supervision information from the label and feature aspects, respectively. To be specific, at the label level, the pairwise constraints are utilized as a kind of typical weak label supervision information. At the feature level, the partial instances collected from multiple perspectives have internal consistency and they are regarded as weak structure supervision information. To achieve a more confident clustering partition, we learn a unified graph with its similarity matrix to incorporate the above two types of weak supervision. On one hand, this similarity matrix is constructed by self-expression across the partial instances collected from multiple perspectives. On the other hand, the pairwise constraints, i.e., must-links and cannot-links, are considered by formulating a regularizer on the similarity matrix. Finally, the clustering results can be directly obtained according to the learned graph, without performing additional clustering techniques. Besides evaluating CSWC on 7 benchmark datasets, we also apply it to the application of face clustering in video data since it has vast application potentiality. Experimental results demonstrate the effectiveness of our algorithm in both incorporating compound weak supervision and identifying faces in real applications.

5.
Chinese Journal of School Health ; (12): 129-132, 2024.
Artículo en Chino | WPRIM (Pacífico Occidental) | ID: wpr-1011377

RESUMEN

Objective@#To determine the heterogeneity for caries prevention service preferences among children in Anhui Province, so as to provide reference for the promotion and popularization of caries prevention services for school age children.@*Methods@#Based on a discrete selection experiment, a face to face questionnaire survey was administered using a multi stage sampling method among 785 parents with children 3-12 years of age who were hospitalized in the stomatology clinics of 7 prefectures and cities in Anhui Province from October 2021 to October 2022. A mixed Logit model was used to evaluate caries prevention service preferences for children.@*Results@#Four discrete choice experiment attributes included in the study were statistically significant for choice preference ( P <0.05). Compared with the control group, parents with a high school education or above preferred caries prevention services with 70%-<80% preventive effectiveness, 2-<5 and <2 km from the service point, and a high service cost ( β =0.38, 1.66, 1.64, 0.00); female parents preferred preventive services with 70%-<80% preventive effectiveness and a high service cost ( β =0.35, 0.01 ); parents of children <7 years of age preferred services with 70%-<80% preventive effectiveness ( β =0.75); parents of children with oral health preferred preventive services during winter and summer vacations ( β =-0.28); parents of children with caries preferred preventive services with a high cost per denticle ( β =0.00)( P <0.05).@*Conclusions@#Parents with different education levels, gender, child age, and oral health status have heterogeneity in dental caries prevention service preferences. The provision of targeted and precise services can improve the participation and coverage of caries prevention services for school age children.

6.
Artículo en Inglés | MEDLINE | ID: mdl-37843750

RESUMEN

Silver nanoparticles (AgNPs) prepared by plants are simple, eco-friendly, and economical. In this study, Magnolia officinalis (MO) extract was applied to synthesize MO@AgNPs. Ultraviolet-visible (UV-vis) spectrum analysis indicated a peak at 440 nm. Most of the particles were spherical with sizes from 1 to approximately 60 nm based on transmission electron microscopy (TEM). X-ray diffraction (XRD) patterns showed a face-centered cubic crystal structure. The zeta value of MO@AgNPs was - 36.5 ± 0.6 mV, which was stable at 25 °C and 4 °C. Growth kinetic studies and the Kirby-Bauer diffusion method showed significant inhibitory activity on Candida albicans (ATCC 10231), Escherichia coli (ATCC BAA-2340), and Staphylococcus aureus (ATCC 25923); the minimum inhibitory concentrations (MIC) were 3, 9, and 9 µg/mL, and corresponding minimum bactericidal concentrations (MBC) were 5, 11, and 9 µg/mL, respectively. MO@AgNPs exhibited better antifungal activity compared to AgNPs prepared using sodium citrate. Further research revealed that MO@AgNPs increased the permeability of bacterial cell membranes. Moreover, the effect of MO@AgNPs on Candida albicans was significantly enhanced by blocking autophagy. The reactive oxygen species (ROS) induced by MO@AgNPs in Candida albicans was limited and may be related to its good antioxidant activity. Finally, MO@AgNPs have no significant cytotoxicity to the human liver LO2 cell line under 20 µg/mL.

7.
Int J Mol Sci ; 24(20)2023 Oct 19.
Artículo en Inglés | MEDLINE | ID: mdl-37895022

RESUMEN

PANoptosis is a newly defined programmed cell death (PCD) triggered by a series of stimuli, and it engages three well-learned PCD forms (pyroptosis, apoptosis, necroptosis) concomitantly. Normally, cell death is recognized as a strategy to eliminate unnecessary cells, inhibit the proliferation of invaded pathogens and maintain homeostasis; however, vigorous cell death can cause excessive inflammation and tissue damage. Acute lung injury (ALI) and chronic obstructive pulmonary syndrome (COPD) exacerbation is related to several pathogens (e.g., influenza A virus, SARS-CoV-2) known to cause PANoptosis. An understanding of the mechanism and specific regulators may help to address the pathological systems of these diseases. This review presents our understanding of the potential mechanism of PANoptosis and the role of PANoptosis in different pulmonary diseases.


Asunto(s)
Lesión Pulmonar Aguda , Apoptosis , Humanos , Muerte Celular , Homeostasis , Inflamación , Piroptosis
8.
Langmuir ; 39(17): 6078-6087, 2023 May 02.
Artículo en Inglés | MEDLINE | ID: mdl-37084417

RESUMEN

Graphitized carbonitride (g-C3N4) is widely used in CO2 reduction, hydrogen production, and degradation of toxic chemical dyes and antibiotics. It is a kind of photocatalytic material with excellent performance, and it has the advantages of being safe and nontoxic, having a suitable band gap (2.7 eV), and having a simple preparation and high stability, but because of its fast optical recombination speed and low visible light overutilization, the multifunctional application of g-C3N4 is seriously hindered. Compared with pure g-C3N4, MWCNTs/g-C3N4 have a red-shift in the visible range and a strong absorption in the visible region. Melamine and carboxylated multiwalled carbon nanotubes were used as raw materials to successfully prepare CMWCNT modified g-C3N4 doped with P, Cl by a high temperature calcination method. The effect of the addition amount of P, Cl on the photocatalytic performance of modified g-C3N4 was studied. The experimental results show that the multiwalled carbon nanotubes can accelerate the electron migration, and the doping of P, Cl elements can change the energy band structure of g-C3N4 and reduce the band gap. Through fluorescence analysis and photocurrent analysis, it is known that the incorporation of P, Cl reduces the recombination efficiency of photogenerated electron-hole pairs. In order to explore the application in the degradation of chemical dyes, the photocatalytic degradation efficiency of RhB under visible light was studied. The photocatalytic performance of the samples was evaluated by photodecomposition of aquatic hydrogen. The results showed that when the amount of ammonium dihydrogen phosphate was 10 wt %, the photocatalytic degradation efficiency was the highest, which was 21.13 times higher than that of g-C3N4.

9.
Environ Sci Pollut Res Int ; 30(39): 90223-90242, 2023 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-37004610

RESUMEN

The pickling sludge produced in the stainless steel pickling process is a hazardous waste and disposal in landfill poses a potential environmental risk. Stainless steel pickling sludge contains metal elements such as Fe, Cr, and Ni and substances such as SiO2 and CaO, which have good value for resource recycling. This paper briefly introduces the generation, nature, and hazards of stainless steel pickling sludge; and clustering analysis of relevant literature keywords in recent years; and detailed analysis and comparison of sludge obtained from different steel mills and resource utilization process. The current situation of pickling sludge resource utilization and the development of relevant policies in China in recent years are summarized, and new thoughts on the direction of its resource utilization are put forward.


Asunto(s)
Aguas del Alcantarillado , Acero Inoxidable , Dióxido de Silicio , Acero , China
10.
Front Aging Neurosci ; 15: 1121152, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-36819723

RESUMEN

Objective: This study aims to investigate novel clinical risk factors for cognitive impairment (CI) in elderly. Methods: A total of 3221 patients (259 patients with CI and 2,962 subjects without CI) were recruited into this nested case-control study who underwent cerebral magnetic resonance angiography (MRA) from 2007 to 2021. All of the clinical data with MRA imaging were recorded followed by standardization processing blindly. The maximum stenosis score of the posterior circulatory artery, including the basilar artery, and bilateral posterior cerebral artery (PCA), was calculated by the cerebral MRA automatic quantitative analysis method. Logistic regression (LR) analysis was used to evaluate the relationship between risk factors and CI. Four machine learning approaches, including LR, decision tree (DT), random forest (RF), and support vector machine (SVM), employing 5-fold cross-validation were used to establish CI predictive models. Results: After matching with age and gender, 208 CI patients and 208 control subjects were finalized the follow-up (3.46 ± 3.19 years) with mean age at 84.47 ± 6.50 years old. Pulse pressure (PP) in first tertile (<58 mmHg) (OR 0.588, 95% confidence interval (CI): 0.362-0.955) was associated with a decreased risk for CI, and ≥50% stenosis of the left PCA (OR 2.854, 95% CI: 1.387-5.872) was associated with an increased risk for CI after adjusting for body mass index, myocardial infarction, and stroke history. Based on the means of various blood pressure (BP) parameters, the performance of the LR, DT, RF and SVM models accurately predicted CI (AUC 0.740, 0.786, 0.762, and 0.753, respectively) after adding the stenosis score of posterior circulatory artery. Conclusion: Elderly with low pulse differential pressure may have lower risk for cognitive impairment. The hybrid model combined with the stenosis score of posterior circulatory artery, clinical indicators, and the means of various BP parameters can effectively predict the risk of CI in elderly individuals.

11.
Psychoradiology ; 3: kkad019, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-38666113

RESUMEN

Catatonia is a psychomotor syndrome that can occur in a broad spectrum of brain disorders, including schizophrenia. Current findings suggest that the neurobiological process underlying catatonia symptoms in schizophrenia is poorly understood. However, emerging neuroimaging studies in catatonia patients have indicated that a disruption in anatomical connectivity of the cortico-striatal-cerebellar system is part of the neurobiology of catatonia, which could serve as a target of neurostimulation such as electroconvulsive therapy and repetitive transcranial magnetic stimulation.

12.
J Colloid Interface Sci ; 620: 478-485, 2022 Aug 15.
Artículo en Inglés | MEDLINE | ID: mdl-35452945

RESUMEN

Though polymer electrolytes have been regarded as promising separators for solid-state lithium metal batteries, their low ionic conductivity, poor thermostability and inflammability limit their practical applications. Herein, a polymer composite electrolyte consisting of metal-organic frameworks modified Ti3C2-MXene nanosheets (ZIF-8@MXene) and polymer mixture (PE-ZIF-8@MXene) was fabricated. The fabricated nonflammable ZIF-8@MXene nanosheets have abundant functional groups and Lewis acid sites as well as high specific surface area. In the composite electrolyte, ZIF-8@MXene nanosheets increased the dissociation of lithium salts and provided channels for transporting ions, accelerating the Li ion transportation. They also enhanced the tensile strength, thermostability and flame resistance of PE-ZIF-8@MXene. Consequently, the fabricated flame-retardant PE-ZIF-8@MXene presented high ionic conductivity (4.4 mS cm-1), impressive Li+ transference number (0.76) and enhanced tensile strength (3.77 MPa). In addition, the assembled Li|PE-ZIF-8@MXene|Li had a long cycle life of 2000 h, and Li|PE-ZIF-8@MXene|LiFePO4 batteries displayed a capacity retention of 89.6% after 500 cycles.

13.
Bioresour Technol ; 344(Pt B): 126312, 2022 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-34767904

RESUMEN

Volatile fatty acids (VFAs) have great potential as cheap raw materials in microbial oil synthesis and reducing the cost of substrates is essential for the development of microbial oil biosynthesis. In this study, the food waste hydrolysate and synthetic VFAs media were both used as substrate to synthesis microbial oil. The optimal short-chain VFAs ratio for microbial oil synthesis is 20:5:5 and increasing the proportion of propionic acid is the key to obtaining odd fatty acids. The hydrolysate obtained from food waste under the total solid condition of 2:1 and pH 5 is the most suitable medium for microbial oil synthesis. The biological products obtained from food waste hydrolysate were comparable to synthetic VFAs media, obtaining a 34.02% of lipid content. Results prove that food waste hydrolysate has great potential as the available feedstock for microbial oil synthesis and a promising application value in food waste recycling.


Asunto(s)
Carbono , Eliminación de Residuos , Ácidos Grasos Volátiles , Fermentación , Alimentos
14.
Comput Struct Biotechnol J ; 19: 3319-3329, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34188780

RESUMEN

Mitochondria, as the energy factory of cells, participate in metabolism processes and play a critical role in the maintenance of human life activities. Mitochondria belong to semi-automatic organelles, which have their own genome different from nuclear genome. Mitochondrial DNA (mtDNA) mutations can cause a series of diseases and threaten human health. However, an effective approach to edit mitochondrial DNA, though long-desired, is lacking. In recent years, gene editing technologies, represented by restriction endonucleases (RE) technology, zinc finger nuclease (ZFN) technology, transcription activator-like effector nuclease (TALEN) technology, CRISPR system and pAgo-based system have been comprehensively explored, but the application of these technologies in mitochondrial gene editing is still to be explored and optimized. The present study highlights the progress and limitations of current mitochondrial gene editing technologies and approaches, and provides insights for development of novel strategies for future attempts.

15.
Chem Commun (Camb) ; 53(26): 3645-3648, 2017 Mar 28.
Artículo en Inglés | MEDLINE | ID: mdl-28243655

RESUMEN

The first two-photon probe, Lyso-OC, was proposed for use in monitoring cell autophagy by detection of the change in the lysosomal polarity during the membrane fusion process of autophagy. The Lyso-OC probe exhibited desirable optical properties and a detection signal that was selective to the polarity change. More importantly, Lyso-OC displayed real-time monitoring of autophagy in living cells.

16.
Biosens Bioelectron ; 77: 921-7, 2016 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-26528806

RESUMEN

A mitochondria-targeted ratiometric two-photon fluorescent probe (Mito-MPVQ) for biological zinc ions detection was developed based on quinolone platform. Mito-MPVQ showed large red shifts (68 nm) and selective ratiometric signal upon Zn(2+) binding. The ratio of emission intensity (I488 nm/I420 nm) increases dramatically from 0.45 to 3.79 (ca. 8-fold). NMR titration and theoretical calculation confirmed the binding of Mito-MPVQ and Zn(2+). Mito-MPVQ also exhibited large two-photon absorption cross sections (150 GM) at nearly 720 nm and insensitivity to pH within the biologically relevant pH range. Cell imaging indicated that Mito-MPVQ could efficiently located in mitochondria and monitor mitochondrial Zn(2+) under two-photon excitation with low cytotoxicity.


Asunto(s)
Colorantes Fluorescentes/síntesis química , Microscopía de Fluorescencia por Excitación Multifotónica/métodos , Mitocondrias/metabolismo , Mitocondrias/ultraestructura , Imagen Molecular/métodos , Zinc/metabolismo , Animales , Células CHO , Cricetulus , Técnicas de Sonda Molecular , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Coloración y Etiquetado/métodos , Zinc/análisis
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA