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1.
Rev Assoc Med Bras (1992) ; 70(4): e20231358, 2024.
Article in English | MEDLINE | ID: mdl-38716944

ABSTRACT

OBJECTIVE: This prospective study aimed to provide a comprehensive analysis of the methylation status of two pivotal genes, CDKN2A/p16INK4A (cyclin-dependent kinase inhibitor 2A) and RB1 (retinoblastoma transcriptional corepressor 1), in breast cancer patients. METHODS: Samples were obtained from 15 women diagnosed with breast cancer and who underwent a total mastectomy. DNA was extracted from the tumor, non-tumor tissue, and peripheral blood (circulating cell-free DNA). The methylation pattern of cell-free DNA extracted from blood collected on the day of mastectomy was compared with the methylation pattern of cell-free DNA from blood collected 1 year post-surgery. The methylation analysis was carried out by sodium bisulfite conversion and polymerase chain reaction, followed by electrophoresis. RESULTS: Methylation of CDKN2A/p16INK4A was identified in 13 tumor samples and 12 non-tumor tissue samples. Two patients exhibited CDKN2A/p16INK4A methylation in the cell-free DNA of the first blood collection, while another showed methylation only in the cell-free DNA of the subsequent blood collection. Regarding RB1, 11 tumors and 8 non-tumor tissue samples presented methylation of the gene. CONCLUSION: This study presents a novel approach for monitoring breast cancer patients through the analysis of cell-free DNA methylation. This analysis can detect changes in methylation patterns before any visible sign of cancer appears in breast tissue and could help predict the recurrence of malignant breast tumors.


Subject(s)
Breast Neoplasms , Cyclin-Dependent Kinase Inhibitor p16 , DNA Methylation , Retinoblastoma Binding Proteins , Adult , Aged , Female , Humans , Middle Aged , Biomarkers, Tumor/genetics , Biomarkers, Tumor/blood , Breast Neoplasms/genetics , Cell-Free Nucleic Acids/genetics , Cell-Free Nucleic Acids/blood , Cell-Free Nucleic Acids/analysis , Cyclin-Dependent Kinase Inhibitor p16/genetics , DNA Methylation/genetics , Mastectomy , Polymerase Chain Reaction , Prospective Studies , Retinoblastoma Binding Proteins/genetics , Ubiquitin-Protein Ligases/genetics
2.
Sao Paulo Med J ; 142(5): e2023140, 2024.
Article in English | MEDLINE | ID: mdl-38747873

ABSTRACT

BACKGROUND: The human telomerase reverse transcriptase (hTERT) enzyme, encoded by the hTERT gene, synthesizes protective telomeric sequences on chromosomes and plays a fundamental role in cancer formation. Methylation of the hTERT gene has an upregulatory effect, increasing hTERT enzyme synthesis and allowing continuous tumor cell division. OBJECTIVE: In a group of patients with breast cancer, we aimed to analyze the methylation status of hTERT in the tumor, surrounding tissue, and circulating free deoxyribonucleic acid (cfDNA) of blood collected on the day of mastectomy and then approximately one year later. DESIGN AND SETTING: A prospective study was conducted at a university hospital in Rio de Janeiro, Brazil. METHODS: Samples were collected from 15 women with breast cancer on the day of mastectomy and approximately one year postoperatively. cfDNA was analyzed by sodium bisulfite conversion, followed by polymerase chain reaction, electrophoresis, and silver nitrate staining. RESULTS: Methylation of hTERT was detected in the tumors and surrounding tissues of all 15 patients. Five patients displayed hTERT methylation in the cfDNA from the blood of the first collection. Of the ten patients who returned for the second collection, three showed methylation. Two patients with methylation in the first collection did not display methylation in the second collection. One patient with no methylation in the first collection displayed methylation in the second collection, and one patient had a diminished level of methylation in the second collection. CONCLUSION: Only one-third of patients displayed methylation in their cfDNA, which may be related to the success of chemotherapy.


Subject(s)
Breast Neoplasms , DNA Methylation , Telomerase , Humans , Telomerase/genetics , Telomerase/blood , Female , Breast Neoplasms/genetics , Breast Neoplasms/blood , Prospective Studies , Middle Aged , Adult , Aged , Biomarkers, Tumor/blood , Biomarkers, Tumor/genetics , Polymerase Chain Reaction , Mastectomy
3.
Toxicon ; 243: 107742, 2024 May 04.
Article in English | MEDLINE | ID: mdl-38705486

ABSTRACT

Phospholipases A2 (PLA2s) from snake venom possess antitumor and antiangiogenic properties. In this study, we evaluated the antimetastatic and antiangiogenic effects of MjTX-II, a Lys49 PLA2 isolated from Bothrops moojeni venom, on lung cancer and endothelial cells. Using in vitro and ex vivo approaches, we demonstrated that MjTX-II reduced cell proliferation and inhibited fundamental processes for lung cancer cells (A549) growth and metastasis, such as adhesion, migration, invasion, and actin cytoskeleton decrease, without significantly interfering with non-tumorigenic lung cells (BEAS-2B). Furthermore, MjTX-II caused cell cycle alterations, increased reactive oxygen species production, modulated the expression of pro- and antiangiogenic genes, and decreased vascular endothelial growth factor (VEGF) expression in HUVECs. Finally, MjTX-II inhibited ex vivo angiogenesis processes in an aortic ring model. Therefore, we conclude that MjTX-II exhibits antimetastatic and antiangiogenic effects in vitro and ex vivo and represents a molecule that hold promise as a pharmacological model for antitumor therapy.

4.
J Psychiatr Res ; 175: 153-159, 2024 May 09.
Article in English | MEDLINE | ID: mdl-38735260

ABSTRACT

We investigated the longitudinal association between physical activity (PA) and symptoms of depression and anxiety in people with depression during the COVID-19 pandemic. We used data from baseline (June 2020) to wave 3 (June 2021) of the PAMPA Cohort, an ambispective cohort with adults in south Brazil. The Hospital Anxiety and Depression Scale assessed depressive and anxiety symptoms in all waves. Participants reported frequency (minutes), type (aerobic, strength, combined), and place (out of home, at home) of physical activity at baseline. Generalized linear models were used to investigate the interaction between time and PA, adjusting for possible confounding variables. Subjective memory decline was assessed using multivariate Cox proportional hazard regression models to obtain adjusted hazard ratio (HR) and respective 95% confidence interval (CI). Participants (n = 424) with self-reported clinically diagnosed depression were included. We observed a non-linear increase trajectory of depression during the first year of the COVID-19 pandemic. PA was associated with a slower trajectory of depressive (slope: -1.89; 95%CI: -3.34, -0.43 points) but not anxiety (slope: -1.33; 95%CI: -2.93, 0.25 points) symptoms during the COVID-19 pandemic. Participants who continued physically active from pre-pandemic in wave 1 showed a lower risk of subjective memory decline during follow-up than those who persisted inactive in the same period (HR: 0.52; 95%CI: 0.30, 0.89). PA attenuated the impact of the COVID-19 pandemic on depressive symptoms in adults living with depression in south Brazil. Regularity of physical activity was associated with fewer depression and anxiety symptoms and a lower risk of subjective memory decline.

5.
Foods ; 13(9)2024 Apr 29.
Article in English | MEDLINE | ID: mdl-38731747

ABSTRACT

This study evaluated the effects of acerola and guava fruit processing co-products fermented with probiotic Lactobacillus acidophilus LA-05 and Lacticaseibacillus paracasei L-10 on the abundance of different intestinal bacterial groups and microbial metabolic activity during 48 h of in vitro fecal fermentation. Digested fermented fruit co-products increased the relative abundance of beneficial bacterial groups while overall decreasing or maintaining the relative abundance of non-beneficial bacterial groups, suggesting selective stimulatory effects on beneficial bacterial intestinal populations. The fermented co-products stimulated microbial metabolic activity due to decreased pH, sugar consumption, short-chain fatty acid production, phenolic compound and metabolic profile alteration, and high antioxidant capacity during fecal fermentation. Acerola and guava co-products have high nutritional value and bioactive compounds whose fermentation with probiotics improves their potential functionalities. The results show that fermented fruit co-products could induce beneficial changes in the relative abundance of several bacterial groups as well as in the metabolic activity of the human intestinal microbiota. These results highlight their potential as novel and circular candidates for use as synbiotic ingredients.

6.
J Nat Prod ; 87(4): 1217-1221, 2024 Apr 26.
Article in English | MEDLINE | ID: mdl-38630559

ABSTRACT

Two unusual naphthoquinones, named here as pleonotoquinones A (1) and B (2), were isolated along with two known anthraquinones (3 and 4) via chromatographic separations of an ethyl acetate extract of the roots of Pleonotoma jasminifolia. Compounds 1 and 2 are the first examples of quinones bearing a 2-methyloxepine moiety. The compounds were isolated with the aid of mass spectrometry and molecular networking, and their structures were resolved using 1D and 2D NMR and HRESIMS data. The isolated compounds were evaluated for their antiproliferative activity against human cancer cell lines, and compounds 1 and 2 displayed cytotoxicity against human colon cancer HCT116 cells (IC50 = 2.6 µM for compound 1 and IC50 = 4.3 µM for compound 2) and human liver cancer HepG2 cells (IC50 = 1.9 µM for compound 1 and IC50 = 6.4 µM for compound 2).


Subject(s)
Antineoplastic Agents, Phytogenic , Drug Screening Assays, Antitumor , Naphthoquinones , Plant Roots , Humans , Naphthoquinones/pharmacology , Naphthoquinones/chemistry , Naphthoquinones/isolation & purification , Antineoplastic Agents, Phytogenic/pharmacology , Antineoplastic Agents, Phytogenic/chemistry , Antineoplastic Agents, Phytogenic/isolation & purification , Molecular Structure , Plant Roots/chemistry , Hep G2 Cells , HCT116 Cells , Boraginaceae/chemistry
7.
Clinics (Sao Paulo) ; 79: 100346, 2024.
Article in English | MEDLINE | ID: mdl-38574572

ABSTRACT

BACKGROUND AND OBJECTIVE: Lower limb varicose veins are a prevalent disease associated with several available treatment options, including conventional surgery and polidocanol foam sclerotherapy. However, few studies have analyzed therapeutic modality outcomes based on Patient-Reported Outcome Measures (PROMs). This large sample-size study was designed to evaluate the outcomes of polidocanol foam sclerotherapy compared to conventional surgery based on an analysis of PROMs. METHODS: This was a prospective, observational, and qualitative study of 205 patients who underwent varicose vein treatment with either polidocanol foam sclerotherapy (57 patients, 90 legs) or conventional surgery (148 patients, 236 legs). Patients were preoperatively assessed and re-evaluated 30 days after the procedure using the Venous Disease Severity Score (VCSS) and specific venous disease quality-of-life questionnaires (VEINES-QoL/Sym). RESULTS: Both treatments significantly improved VCSS and VEINES results 30 days after the procedure (p < 0.05). However, surgery promoted greater improvements in VCSS (on average 4.02-points improvement, p < 0.001), VEINES-QoL (average 8-points improvement, p < 0.001), and VEINES-Sym (average 11.66 points improvement, p < 0.001) than did sclerotherapy. Postoperative pain and aesthetic concerns about the legs were the domains of the questionnaires in which the results varied the most between the treatment modalities, with worse results for sclerotherapy. CONCLUSION: Both polidocanol foam sclerotherapy and conventional surgery positively impact patients' quality of life after 30 days, but the improvement is more significant for patients who undergo conventional surgery.


Subject(s)
Quality of Life , Varicose Veins , Humans , Polidocanol , Polyethylene Glycols , Prospective Studies , Saphenous Vein , Sclerosing Solutions/therapeutic use , Sclerosing Solutions/adverse effects , Sclerotherapy/adverse effects , Treatment Outcome , Varicose Veins/surgery , Varicose Veins/therapy
8.
Cytogenet Genome Res ; 2024 Apr 17.
Article in English | MEDLINE | ID: mdl-38631304

ABSTRACT

Introduction Eukaryotic genomes consist of both single and repetitive sequences, including Satellite DNAs (satDNA), which are non-coding sequences arranged in tandem arrays. These sequences play a crucial role in genomic functions and innovations, influencing processes such as nuclear material maintenance, heterochromatin formation, and sex chromosome differentiation. In this genomic era, advancements in next-generation sequencing and bioinformatic tools have facilitated the comprehensive cataloging of repetitive elements in genomes, particularly in non-model species. This study focuses on the satellitome of Ancistrus sp., a diverse fish species within the Loricariidae family. The genus Ancistrus displays significant karyotypic evolution, with deviations from the ancestral diploid number. Methods Using bioinformatic approaches, we identified 40 satellite DNA families in Ancistrus sp., constituting 5.19% of the genome. The abundance and divergence landscape analysis revealed diverse profiles, indicating recent amplification and homogenization of these satDNA sequences. Results The most abundant satellite, AnSat1-142, constitutes 2.1% of the genome, while the least abundant, AnSat40-52, represents 0.0034%. The monomer repeat length ranges from 16 to 142 base pairs, with an average length of 61 bp. These findings contribute to understanding the genomic dynamics and evolution of satDNAs in Ancistrus sp. Conclusion The study underscores the variability in satDNAs among fish species and provides valuable insights into the chromosomal organization and evolution of repetitive elements in non-model organisms.

10.
J Esthet Restor Dent ; 2024 Apr 06.
Article in English | MEDLINE | ID: mdl-38581272

ABSTRACT

OBJECTIVE: To evaluate the effect of fluoride consistency and composition to protect enamel and dentin against the dental erosion. MATERIALS AND METHODS: Bovine enamel and dentin specimens were treated with artificial saliva, neutral fluoride gel (NFG), acidulated phosphate fluoride gel (AFG), neutral fluoride foam (NFF), and acidulated phosphate fluoride foam. The samples were subjected to cycling. Micro energy-dispersive X-ray fluorescence spectrometry, surface roughness (Ra), contact angle (CA), and scanning electron microscopy (SEM) were performed. Composition, CA and Ra data were analyzed by ANOVA and multiple comparison test (p < 0.05). RESULTS: The dentin protected had a significantly higher mineral content than in the control. Eroded unprotected enamel had higher Ra values than normal surfaces. Fluoride treatments increased the Ra in dentin samples. AFG increased the CA in enamel. Fluoride foams increased CA in dentin with reduced mineral loss. SEM analysis found a deposited layer on enamel treated with AFG and remnants of deposits on dentin treated with NFG and NFF. CONCLUSION: Regardless of the form of application, fluoride provided protection against erosion, however with different levels. CLINICAL SIGNIFICANCE: Applying the adequate fluoride form is relevant since the formulations have different effects on both enamel and dentin.

11.
J Esthet Restor Dent ; 2024 Apr 02.
Article in English | MEDLINE | ID: mdl-38563466

ABSTRACT

OBJECTIVE: This systematic review aimed to analyze the clinical (survival rate, failure risk, or fracture) and laboratory performance (fracture mode or failure) of rehabilitations of endodontically treated teeth, with and without posts. MATERIALS AND METHODS: A systematic search was conducted in the Pubmed, Scopus, Web of Science, Embase, Cochrane Library, and OpenGrey databases up to March 2023, according to PRISMA guidelines. In vitro and clinical studies that compared the clinical and laboratory performance of endodontically treated teeth with and without intraradicular posts were included. Studies selection, data extraction, and risk of bias analysis were performed. RESULTS: Thirty-one in vitro and 7 clinical studies were included. For in vitro studies, fiberglass post (n = 24) was the most mentioned. The follow-up time of the clinical studies ranged from 1 to 17 years, with the fiber-reinforced composite post (n = 3) being the most evaluated, and only failure risk proved to be more favorable for using intraradicular posts. CONCLUSION: Rehabilitations of endodontically treated teeth with and without intraradicular retainers showed no difference in fracture resistance and failure mode, evaluated by in vitro studies. Clinical studies showed no difference in survival rate, but failure risk proved to be more favorable for the use of posts. CLINICAL SIGNIFICANCE: This analysis revealed significant variability between results, however, most laboratory and clinical studies revealed no difference with using the post. Furthermore, it is important to emphasize the need to evaluate the coronary remnant and the general characteristics of the tooth in each situation.

12.
Article in English | MEDLINE | ID: mdl-38688175

ABSTRACT

The present work aimed at the development and characterization of aroeira leaf flour (Schinus terebinthifolius Raddi), obtained by lyophilization and drying in an air circulation oven. The technological, physical, physico-chemical, morphological, functional, and microbiological aspects were analyzed. Physico-chemical analysis identified the following properties with values provided respectively for fresh leaves (FOin) and flours (FES and FLIO): low water activity (0.984, 0.370, 0.387 g/100 g), moisture (64.52, 5.37, 7.97 g /100 g), ash (2.69, 6.51, and 6.89 g/100 g), pH (0.89, 4.45, 4.48 g/100 g), lipids (0.84, 1.67, 5.23 g/100 g), protein (3.29, 8.23, 14.12 g/100 g), carbohydrates (17.02, 53.12, 33.02 g/100 g), ascorbic acid (19.70, 34.20, 36.90 mg/100 g). Sources of fiber from plant leaves and flours (11.64, 25.1, 32.89 g/100 g) showed increased levels of luminosity. For NMR, the presence of aliphatic and aromatic compounds with olefinic hydrogens and a derivative of gallic acid were detected. The most abundant minerals detected were potassium and calcium. Micrographs identified the presence of irregular, non-uniform, and sponge-like particles. The main sugars detected were: fructose, glucose, and maltose. Malic, succinic, citric, lactic, and formic acids were found. Fifteen phenolic compounds were identified in the samples, highlighting: kaempferol, catechin, and caffeic acid. The values ​​found for phenolics were (447, 716.66, 493.31 mg EAG/100 g), flavonoids (267.60, 267.60, 286.26 EC/100 g). Antioxidant activity was higher using the ABTS method rather than FRAP for analysis of FOin, FES, and FLIO. Since the flours of the aroeira leaf have an abundant matrix of nutrients with bioactive properties and antioxidant activity, they have a potential for technological and functional use when added to food.


Subject(s)
Anacardiaceae , Flour , Plant Leaves , Plant Leaves/chemistry , Anacardiaceae/chemistry , Flour/analysis , Freeze Drying , Carbohydrates/analysis , Carbohydrates/chemistry , Antioxidants/analysis , Antioxidants/chemistry , Schinus
13.
Journal of Electronics and Electrical Engineering ; 3(1): 148-165, mar.2024. ilus, graf
Article in English | CONASS, Sec. Est. Saúde SP, SESSP-IDPCPROD, Sec. Est. Saúde SP | ID: biblio-1537914

ABSTRACT

Ventricular Assist Devices (VADs) play a crucial role in both bridging to transplantation and serving as destination therapy for congestive heart failure (CHF) management. This study aims to address the limitations of existing control strategies for VADs, specifically their inability to adapt automatically to hemodynamic changes. It proposes a novel embedded cyber-physical system (CPS) based on real-time data processing, reconfigurable architecture, and communication protocols aligned with Health 4.0 concepts to enhance physiological control over VADs (PC-VAD). The research employs a multi-objective PC-VAD approach within a hybrid cardiovascular simulator. An embedded CPS is introduced to overcome challenges related to differences in controller characteristics between computers and embedded systems. The study assesses the performance of the embedded CPS by comparing it with a computer-based control system. The embedded CPS demonstrates outcomes comparable to the computer-based control system, maintaining mean arterial pressure and cardiac output at physiological levels. Even in the face of variations in ejection fraction, the embedded CPS dynamically adjusts the pump's rotational speed based on simulated clinical conditions. Notably, there is no aortic reflux to the ventricle through the VAD during testing. These findings affirm the satisfactory control performance of the embedded CPS in regulating VADs. The study concludes that the embedded CPS effectively addresses the limitations of current VAD control strategies, exhibiting control performance comparable to computer-based systems. However, further experimentation and in vivo studies are necessary to validate and ensure its applicability in real-world scenarios.


Subject(s)
Heart-Assist Devices , Heart Failure
14.
Biochem Biophys Res Commun ; 706: 149748, 2024 Apr 30.
Article in English | MEDLINE | ID: mdl-38460450

ABSTRACT

Angiogenesis is a process that is controlled by a delicate combination of proangiogenic and antiangiogenic molecules and can be disrupted in various illnesses, including cancer. Non-cancerous diseases can also have an abnormal or insufficient vascular growth, inflammation and hypoxia, which exacerbate angiogenesis. These conditions include atherosclerosis, psoriasis, endometriosis, asthma, obesity and AIDS. Based on that, the present work assessed the in vitro and ex vivo antiangiogenic properties stemming from BthMP, a P-I metalloproteinase from Bothrops moojeni snake venom, via the VEGF pathway. BthMP at a concentration of 5 and 40 µg/mL showed no toxicity to endothelial cells (HUVEC) in the MTT assay and was not able to induce necrosis and colony proliferation. Interestingly, BthMP inhibited adhesion, migration and invasion of HUVECs in Matrigel and arrested in vitro angiogenesis by reducing the average number of nodules in toxin-treated cells by 9.6 and 17.32 at 5 and 40 µg/mL, respectively, and the number of tubules by 15.9 at 5 µg/mL and 21.6 at 40 µg/mL in a VEGF-dependent way, an essential proangiogenic property. Furthermore, BthMP inhibited the occurrence of the angiogenic process in an ex vivo aortic ring test by decreasing new vessel formation by 52% at 5 µg/mL and by 66% at 40 µg/mL and by increasing the expression of an antiangiogenic gene, SFLT-1, and decreasing the expression of the proangiogenic genes VEGFA and ANGPT-1. Finally, this toxin reduces the production of nitric oxide, a marker that promotes angiogenesis and VEGF modulation, and decreases the protein expression of VEGFA in the supernatant of the HUVEC culture by about 30 %. These results suggest that BthMP has a promising antiangiogenic property and proves to be a biotechnological mechanism for understanding the antiangiogenic responses induced by snake venom metalloproteinases, which could be applied to a variety of diseases that exhibit an imbalance of angiogenesis mechanisms.


Subject(s)
Bothrops , Endothelial Cells , Venomous Snakes , Animals , Female , Humans , Endothelial Cells/metabolism , Vascular Endothelial Growth Factor A/metabolism , Bothrops/metabolism , Metalloproteases/metabolism , Snake Venoms , Human Umbilical Vein Endothelial Cells/metabolism , Angiogenesis Inhibitors/pharmacology
15.
Cancer Discov ; 2024 Mar 27.
Article in English | MEDLINE | ID: mdl-38533987

ABSTRACT

Cancer homeostasis depends on a balance between activated oncogenic pathways driving tumorigenesis and engagement of stress-response programs that counteract the inherent toxicity of such aberrant signaling. While inhibition of oncogenic signaling pathways has been explored extensively, there is increasing evidence that overactivation of the same pathways can also disrupt cancer homeostasis and cause lethality. We show here that inhibition of Protein Phosphatase 2A (PP2A) hyperactivates multiple oncogenic pathways and engages stress responses in colon cancer cells. Genetic and compound screens identify combined inhibition of PP2A and WEE1 as synergistic in multiple cancer models by collapsing DNA replication and triggering premature mitosis followed by cell death. This combination also suppressed the growth of patient-derived tumors in vivo. Remarkably, acquired resistance to this drug combination suppressed the ability of colon cancer cells to form tumors in vivo. Our data suggest that paradoxical activation of oncogenic signaling can result in tumor suppressive resistance.

16.
Chromosoma ; 2024 Mar 28.
Article in English | MEDLINE | ID: mdl-38546866

ABSTRACT

Among the repetitive elements, satellite DNA (SatDNA) emerges as extensive arrays of highly similar tandemly repeated units, spanning megabases in length. Given that the satDNA PboSat01-176, previously characterized in P. boiei, prompted our interest for having a high abundance in P. boiei and potential for centromeric satellite, here, we employed various approaches, including low coverage genome sequencing, followed by computational analysis and chromosomal localization techniques in four Proceratophrys species and, investigating the genomic presence and sharing, as well as its potential for chromosomal centromere marker in Proceratophrys frog species. Our findings demonstrate that PboSat01-176 exhibits high abundance across all four Proceratophrys species, displaying distinct characteristics that establish it as the predominant repetitive DNA element in these species. The satellite DNA is prominently clustered in the peri/centromeric region of the chromosomes, particularly in the heterochromatic regions. The widespread presence of PboSat01-176 in closely related Proceratophrys species reinforces the validity of the library hypothesis for repetitive sequences. Thus, this study highlighted the utility of the satDNA family PboSat01-176 as a reliable centromeric marker in Proceratophrys species, with potential to be applied in other species of anuran amphibians. The observed sharing and maintenance of this sequence within the genus suggest possibilities for future research, particularly through expanded sampling to elucidate parameters that underlie the library hypothesis and the evolutionary dynamics of satDNA sequences.

17.
Heliyon ; 10(5): e26819, 2024 Mar 15.
Article in English | MEDLINE | ID: mdl-38439847

ABSTRACT

Nitrogen is one of the essential nutrients for the production of agricultural crops, participating in a complex interaction among soil, plant and the atmosphere. Therefore, its monitoring is important both economically and environmentally. The aim of this work was to estimate the leaf nitrogen contents in sugarcane from hyperspectral reflectance data during different vegetative stages of the plant. The assessments were performed from an experiment designed in completely randomized blocks, with increasing nitrogen doses (0, 60, 120 and 180 kg ha-1). The acquisition of the spectral data occurred at different stages of crop development (67, 99, 144, 164, 200, 228, 255 and 313 days after cutting; DAC). In the laboratory, the hyperspectral responses of the leaves and the Leaf Nitrogen Contents (LNC) were obtained. The hyperspectral data and the LNC values were used to generate spectral models employing the technique of Partial Least Squares Regression (PLSR) Analysis, also with the calculation of the spectral bands of greatest relevance, by the Variable Importance in Projection (VIP). In general, the increase in LNC promoted a smaller reflectance in all wavelengths in the visible (400-680 nm). Acceptable models were obtained (R2 > 0.70 and RMSE <1.41 g kg-1), the most robust of which were those generated from spectra in the visible (400-680 nm) and red-edge (680-750 nm), with values of R2 > 0.81 and RMSE <1.24 g kg-1. An independent validation, leave-one-date-out cross validation (LOOCV), was performed using data from other collections, which confirmed the robustness and the possibility of LNC prediction in new data sets, derived, for instance, from samplings subsequent to the period of study.

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