Publications by authors named "Gustavo Chaves"

14 Publications

  • Page 1 of 1

Late discolouration of root-treated teeth and subsequent restorative retreatment: three case reports.

Aust Endod J 2021 Oct 12. Epub 2021 Oct 12.

Department of Restorative Dentistry and Esthetic, Brazilian Dentistry Association - Section of Goiás, Goiânia, Brazil.

Root-filled teeth that receive ceramic veneers may experience subsequent coronal discolouration, which will likely negatively affect the quality of life of patients and their relationship with the clinician. This manuscript describes three cases of this undesirable aesthetic consequence in anterior teeth of young patients and the subsequent restorative reintervention, with satisfactory results. In all three reports, the root canal filling was performed using cements containing bismuth oxide that likely disassociated into reduced metallic crystals when in contact with LED light. The discolouration observed after veneer cementation was most likely caused by the accumulation of these bismuth metallic crystals. These cases highlight the importance of preventing this undesirable complication, which may also result in the potential subsequent further sacrifice of sound coronal dental structure, and the role of recall in aesthetically demanding clinical cases.
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http://dx.doi.org/10.1111/aej.12581DOI Listing
October 2021

Behaviour and animal welfare indicators of broiler chickens housed in an enriched environment.

PLoS One 2021 27;16(9):e0256963. Epub 2021 Sep 27.

Department of Rural Engineering, School of Agronomic Science (FCA), São Paulo State University "Júlio de Mesquita Filho" (UNESP), Botucatu, São Paulo, Brazil.

The present study aimed to assess the influence of adding straw bales, step platforms, and laser projectors as environmental enrichment resources on the behaviour and welfare indicators of broiler chickens (Gallus gallus domesticus). A sample of 4,000 day-old male Cobb® 500 birds was used. The experimental treatments consisted of No Environmental Enrichment (NEE)-similar to a conventional environment; and Environmental Enrichment (EE)-environment enriched with straw bales, step platforms, and laser projectors, with four replicates per treatment of 500 animals. Behavioural characteristics (ethological observation through cameras, grab test, and modified touch test) and animal welfare indicators (pododermatitis and dorsal cranial myopathy) were assessed. The birds submitted to the EE treatment exhibited greater exploratory activity and expression of behaviours associated with comfort and welfare, whereas those in the NEE group were less active. Locomotion and play fighting behaviour decreased and behaviours associated with comfort increased as age advanced. The frequencies of interaction with laser spots and birds lying around straw bales were the highest in the 1st week (P<0.01). The behaviours of pecking at straw bales (P<0.0004), using the step platforms (P = 0.0001) and being on top of straw bales (P<0.0002) gradually increased. The chickens accessed the feeding troughs the most in the period of 0800 hours (P<0.0001) and expressed the highest frequencies of behaviours associated with comfort in the 1400 hours and 1700 hours periods. The birds in the EE group were calmer in face of human presence and touch and scored higher in animal welfare indicators. Adding straw bales, step platforms, and laser projectors increased locomotion, reduced expression of fear, and improved animal welfare indicators of broiler chickens.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0256963PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8476007PMC
September 2021

Zinc accelerates respiratory burst termination in human PMN.

Redox Biol 2021 Sep 17;47:102133. Epub 2021 Sep 17.

Center of Physiology, Pathophysiology and Biophysics, Paracelsus Medical University, Nuremberg, Germany; Center of Physiology, Pathophysiology and Biophysics, Paracelsus Medical University, Salzburg, Austria. Electronic address:

The respiratory burst of phagocytes is essential for human survival. Innate immune defence against pathogens relies strongly on reactive oxygen species (ROS) production by the NADPH oxidase (NOX2). ROS kill pathogens while the translocation of electrons across the plasma membrane via NOX2 depolarizes the cell. Simultaneously, protons are released into the cytosol. Here, we compare freshly isolated human polymorphonuclear leukocytes (PMN) to the granulocytes-like cell line PLB 985. We are recording ROS production while inhibiting the charge compensating and pH regulating voltage-gated proton channel (H1). The data suggests that human PMN and the PLB 985 generate ROS via a general mechanism, consistent of NOX2 and H1. Additionally, we advanced a mathematical model based on the biophysical properties of NOX2 and H1. Our results strongly suggest the essential interconnection of H1 and NOX2 during the respiratory burst of phagocytes. Zinc chelation during the time course of the experiments postulates that zinc leads to an irreversible termination of the respiratory burst over time. Flow cytometry shows cell death triggered by high zinc concentrations and PMA. Our data might help to elucidate the complex interaction of proteins during the respiratory burst and contribute to decipher its termination.
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http://dx.doi.org/10.1016/j.redox.2021.102133DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8476447PMC
September 2021

Announcing the call for the Issue Focus on the 2nd Costa Rican Biophysics Symposium-virtual meeting, March 2021.

Biophys Rev 2021 Jul 6:1-2. Epub 2021 Jul 6.

Escuela de Química, Universidad Nacional de Costa Rica, Heredia, Costa Rica.

This Commentary is a call for submissions for the upcoming Issue Focus that will highlight some of the scientific topics discussed during the 2 Costa Rica Biophysics Symposium.
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http://dx.doi.org/10.1007/s12551-021-00816-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8259767PMC
July 2021

Guided endodontics: The impact of new technologies on complex case solution.

Aust Endod J 2021 Mar 3. Epub 2021 Mar 3.

School of Dentistry, Federal University of Goiás, Goiânia, Brazil.

Discuss the impact of new diagnostic and planning technologies on the resolution of a clinical case of an upper central incisor with lateral perforation, root canal calcification and apical periodontitis. A 44-year-old woman sought treatment because of a colour change in an anterior tooth. The tooth had already been endodontically accessed, and she reported that two different clinicians had failed to locate the root canal. A Cone Beam Computed Tomography scan showed excessive wear and root perforation in the middle third, as well as pulp canal obliteration in the apical third. The perforation was treated using a biomaterial, and the root canal was located using guided endodontics. This treatment protocol was used to access, prepare, medicate with calcium hydroxide for 21 days and fill the root canal. Treatment results were satisfactory at 6-month follow-up.
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http://dx.doi.org/10.1111/aej.12498DOI Listing
March 2021

Guided Endodontics: Volume of Dental Tissue Removed by Guided Access Cavity Preparation-An Ex Vivo Study.

J Endod 2020 Dec 16;46(12):1907-1912. Epub 2020 Sep 16.

Faculdade de Odontologia, Universidade Federal de Goiás, Goiânia, Goiás, Brazil.

Introduction: Guided endodontics emerged as an alternative method capable of providing greater precision and accuracy to endodontic treatments. The aim of the present study was to compare the volume of dental tissue removed after guided endodontic access (GEA) and conventional endodontic access (CEA) to mandibular incisors and upper molars.

Methods: Twenty extracted human mandibular incisors and upper molars were selected and submitted to cone-beam computed tomographic (CBCT) examination. They were divided into 2 groups, G1 (mandibular incisors) and G2 (maxillary molars), and subdivided into G1a (CEA), G1b (GEA), G2a (CEA), and G2b (GEA). The Digital Imaging and Communications in Medicine files obtained by examining the CBCT scans were transferred to InVesalius software (Renato Archer Information Technology Center, Campinas, SP, Brazil) to calculate the initial volume of each tooth. G1b and G2b teeth were scanned with a device to plan and print the guides. After gaining endodontic access, new CBCT examinations were performed to calculate the final volume of each sample unit. The Student t test for independent samples compared the volumes among the groups.

Results: G1 group had an average volume reduction of 31.667 mm (10.62%) using CEA and 26.523 mm (10.65%) using GEA with no significant difference among the groups (P = .960). There was an average volume reduction of 62.526 mm (5.86%) in the G2 group using CEA and 45.677 mm (4.11%) using GEA with a significant difference among the groups (P = .004).

Conclusions: GEA preserved a greater volume of dental tissue in extracted upper human molars than CEA; however, there was no significant difference between CEA and GEA in the volume of dental tissue removed from mandibular incisors.
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http://dx.doi.org/10.1016/j.joen.2020.09.008DOI Listing
December 2020

Zinc modulation of proton currents in a new voltage-gated proton channel suggests a mechanism of inhibition.

FEBS J 2020 11 6;287(22):4996-5018. Epub 2020 Apr 6.

Institut für Physiologie und Pathophysiologie, Paracelsus Universität Salzburg Standort Nürnberg, Nuremberg, Germany.

The H 1 voltage-gated proton (H 1) channel is a key component of the cellular proton extrusion machinery and is pivotal for charge compensation during the respiratory burst of phagocytes. The best-described physiological inhibitor of H 1 is Zn . Externally applied ZnCl drastically reduces proton currents reportedly recorded in Homo sapiens, Rattus norvegicus, Mus musculus, Oryctolagus cuniculus, Rana esculenta, Helix aspersa, Ciona intestinalis, Coccolithus pelagicus, Emiliania huxleyi, Danio rerio, Helisoma trivolvis, and Lingulodinium polyedrum, but with considerable species variability. Here, we report the effects of Zn and Cd on H 1 from Nicoletia phytophila, NpH 1. We introduced mutations at potential Zn coordination sites and measured Zn inhibition in different extracellular pH, with Zn concentrations up to 1000 μm. Zn inhibition in NpH 1 was quantified by the slowing of the activation time constant and a positive shift of the conductance-voltage curve. Replacing aspartate in the S3-S4 loop with histidine (D145H) enhanced both the slowing of activation kinetics and the shift in the voltage-conductance curve, such that Zn inhibition closely resembled that of the human channel. Histidine is much more effective than aspartate in coordinating Zn in the S3-S4 linker. A simple Hodgkin Huxley model of NpH 1 suggests a decrease in the opening rate if it is inhibited by zinc or cadmium. Limiting slope measurements and high-resolution clear native gel electrophoresis (hrCNE) confirmed that NpH 1 functions as a dimer. The data support the hypothesis that zinc is coordinated in between the dimer instead of the monomer. Zinc coordination sites may be potential targets for drug development.
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http://dx.doi.org/10.1111/febs.15291DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7754295PMC
November 2020

Assessing Structural Determinants of Zn Binding to Human H1 via Multiple MD Simulations.

Biophys J 2020 03 11;118(5):1221-1233. Epub 2020 Jan 11.

Institute of Physiology and Pathophysiology, Klinikum Nuremberg Medical School, Paracelsus Medical University, Nuremberg, Germany. Electronic address:

Voltage-gated proton channels (H1) are essential for various physiological tasks but are strongly inhibited by Zn cations. Some determinants of Zn binding have been elucidated experimentally and in computational studies. However, the results have always been interpreted under the assumption that Zn binds to monomeric H1 despite evidence that H1 expresses as a dimer and that the dimer has a higher affinity for zinc than the monomer and experimental data that suggest coordination in the dimer interface. The results of former studies are also controversial, e.g., supporting either one single or two binding sites. Some structural determinants of the binding are still elusive. We performed a series of molecular dynamics simulations to address different structures of the human proton channel, the monomer and two plausible dimer conformations, to compare their respective potential to interact with and bind Zn via the essential histidines. The series consisted of several copies of the system to generate independent trajectories and increase the significance compared to a single simulation. The amount of time simulated totals 29.9 μs for 126 simulations of systems comprising ∼59,000 to ∼187,000 atoms. Our approach confirms the existence of two binding sites in monomeric and dimeric human H1. The dimer interface is more efficient for attracting and binding Zn via the essential histidines than the monomer or a dimer with the histidines in the periphery. The higher affinity is due to the residues in the dimer interface that create an attractive electrostatic potential funneling the zinc cations toward the binding sites.
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http://dx.doi.org/10.1016/j.bpj.2019.12.035DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7063441PMC
March 2020

Identification of an HV 1 voltage-gated proton channel in insects.

FEBS J 2016 Apr 6;283(8):1453-64. Epub 2016 Mar 6.

Institute of Complex Systems, Zelluläre Biophysik (ICS-4) Forschungszentrum Jülich, Germany.

Unlabelled: The voltage-gated proton channel 1 (HV 1) is an important component of the cellular proton extrusion machinery and is essential for charge compensation during the respiratory burst of phagocytes. HV 1 has been identified in a wide range of eukaryotes throughout the animal kingdom, with the exception of insects. Therefore, it has been proposed that insects do not possess an HV 1 channel. In the present study, we report the existence of an HV 1-type proton channel in insects. We searched insect transcriptome shotgun assembly (TSA) sequence databases and found putative HV 1 orthologues in various polyneopteran insects. To confirm that these putative HV 1 orthologues were functional channels, we studied the HV 1 channel of Nicoletia phytophila (NpHV 1), an insect of the Zygentoma order, in more detail. NpHV 1 comprises 239 amino acids and is 33% identical to the human voltage-gated proton channel 1. Patch clamp measurements in a heterologous expression system showed proton selectivity, as well as pH- and voltage-dependent gating. Interestingly, NpHV 1 shows slightly enhanced pH-dependent gating compared to the human channel. Mutations in the first transmembrane segment at position 66 (Asp66), the presumed selectivity filter, lead to a loss of proton-selective conduction, confirming the importance of this aspartate residue in voltage-gated proton channels.

Database: Nucleotide sequence data have been deposited in the GenBank database under accession number KT780722.
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http://dx.doi.org/10.1111/febs.13680DOI Listing
April 2016

Tryptophan 207 is crucial to the unique properties of the human voltage-gated proton channel, hHV1.

J Gen Physiol 2015 Nov 12;146(5):343-56. Epub 2015 Oct 12.

Department of Molecular Biophysics and Physiology, Rush University, Chicago, IL 60612

Part of the "signature sequence" that defines the voltage-gated proton channel (H(V1)) is a tryptophan residue adjacent to the second Arg in the S4 transmembrane helix: RxWRxxR, which is perfectly conserved in all high confidence H(V1) genes. Replacing Trp207 in human HV1 (hH(V1)) with Ala, Ser, or Phe facilitated gating, accelerating channel opening by 100-fold, and closing by 30-fold. Mutant channels opened at more negative voltages than wild-type (WT) channels, indicating that in WT channels, Trp favors a closed state. The Arrhenius activation energy, Ea, for channel opening decreased to 22 kcal/mol from 30-38 kcal/mol for WT, confirming that Trp207 establishes the major energy barrier between closed and open hH(V1). Cation-π interaction between Trp207 and Arg211 evidently latches the channel closed. Trp207 mutants lost proton selectivity at pHo >8.0. Finally, gating that depends on the transmembrane pH gradient (ΔpH-dependent gating), a universal feature of H(V1) that is essential to its biological functions, was compromised. In the WT hH(V1), ΔpH-dependent gating is shown to saturate above pHi or pHo 8, consistent with a single pH sensor with alternating access to internal and external solutions. However, saturation occurred independently of ΔpH, indicating the existence of distinct internal and external pH sensors. In Trp207 mutants, ΔpH-dependent gating saturated at lower pHo but not at lower pHi. That Trp207 mutation selectively alters pHo sensing further supports the existence of distinct internal and external pH sensors. Analogous mutations in H(V1) from the unicellular species Karlodinium veneficum and Emiliania huxleyi produced generally similar consequences. Saturation of ΔpH-dependent gating occurred at the same pHo and pHi in H(V1) of all three species, suggesting that the same or similar group(s) is involved in pH sensing. Therefore, Trp enables four characteristic properties: slow channel opening, highly temperature-dependent gating kinetics, proton selectivity, and ΔpH-dependent gating.
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http://dx.doi.org/10.1085/jgp.201511456DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4621752PMC
November 2015

Synergistic approach to elucidate the incorporation of magnesium ions into hydroxyapatite.

Chemistry 2015 Feb 12;21(6):2537-46. Epub 2014 Dec 12.

Departament de Física Aplicada, EEI, Universitat Politècnica de Catalunya, Av. Pla de la Massa, 8, 08700 Igualada (Spain).

Although the content of Mg(2+) in hard tissues is very low (typically ≤1.5 wt %), its incorporation into synthetic hydroxyapatite (HAp) particles and its role in the mineral's properties are still subject of intensive debate. A combined experimental-computational approach is used to answer many of the open questions. Mg(2+) -enriched HAp particles are prepared using different synthetic approaches and considering different concentrations of Mg(2+) in the reaction medium. The composition, morphology and structure of the resulting particles are investigated using X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, scanning and transmission electron microscopies, FTIR, and wide-angle X-ray diffraction. After this scrutiny, the role of the Mg(2+) in the first nucleation stages, before HAp formation, is investigated using atomistic molecular dynamics simulations. Saturated solutions are simulated with and without the presence of DNA, which has been recently used as a soft template in the biomineralization process. This synergistic investigation provides a complete picture of how Mg(2+) ions affect the mineralization from the first stages onwards.
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http://dx.doi.org/10.1002/chem.201405428DOI Listing
February 2015

DNA adsorbed on hydroxyapatite surfaces.

J Mater Chem B 2014 Oct 10;2(40):6953-6966. Epub 2014 Sep 10.

Departament d'Enginyeria Química, E. T. S. d'Enginyeria Industrial de Barcelona, Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona, Spain.

Hydroxyapatite (HAp) particles with very different surface charges and compositions (i.e. different Ca/P and CO /PO ratios) have been obtained by varying the experimental conditions used during the chemical precipitation process. The DNA adsorption capacity and protection imparted against the attack of nucleases of HAp particles have been proved to depend on the surface charge while the buffering capacity is affected by the chemical composition. On the basis of both the surface charge and the crystallinity, the predominant planes at the surfaces of HAp particles have been identified. Atomistic molecular dynamics simulations of surfaces constructed with these planes (i.e. (001) and the two terminations of (010)) with the adsorbed B-DNA double helix have been performed to get microscopic understanding of the influence of the mineral in the biomolecule structure and the interaction energies. The results indicate that the DNA secondary structure is perfectly preserved on the (001) surface, this stability being accompanied by an attractive binding energy. In contrast, the (010) surface with PO , OH and Ca ions in the termination induces significant local and global deformations in the double helix, repulsive OH(HAp)PO (DNA) interactions provoking the desorption of the biomolecule. Finally, although the termination of the (010) surface with PO and Ca ions also deforms the double helix, it forms very strong attractive interactions with the biomolecule. These binding characteristics are in excellent agreement with the DNA adsorption and protection abilities experimentally determined for the HAp samples. Finally, the surface charge has been found less decisive than the chemical composition in the efficacy of the transfection process.
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http://dx.doi.org/10.1039/c4tb01184hDOI Listing
October 2014

Effect of gutta-percha solvents on fiberglass post bond strength to root canal dentin.

J Oral Sci 2014 Jun;56(2):105-12

Endodontic Division, School of Dentistry, University of Cuiabá

The purpose of this study was to investigate the influence of gutta-percha solvents on the bond strength of fiberglass post to root canal dentin. Forty bovine incisors were decoronated, prepared, filled, and randomly distributed into four groups (n = 10) according to the gutta-percha solvent used: control, xylene, eucalyptol and orange oil. After root canal treatment, the posts were cemented into the prepared root canals using a resin-based cement. A micro push-out test was executed, and the patterns of failure were assessed with microscopy. The data were analyzed using two-way ANOVA followed by Tukey's test. The control group exhibited greater bond strength compared to the eucalyptol group in the cervical and middle thirds of the root (P < 0.05); however, it did not differ significantly from the xylene and orange oil groups (P > 0.05). No difference was observed in the values of the xylene, orange oil, and eucalyptol groups (P > 0.05). The cervical third had higher values than the apical third for all tested solvents (P < 0.05). Adhesive failure between resin cement and dentin was the most frequent type of failure. The use of xylene and orange oil as gutta-percha solvents did not influence the bond strength of fiberglass posts to root canal dentin.
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http://dx.doi.org/10.2334/josnusd.56.105DOI Listing
June 2014

Mineralization of DNA into nanoparticles of hydroxyapatite.

Dalton Trans 2014 Jan;43(1):317-27

Departament de Física Aplicada, EEI, Universitat Politècnica de Catalunya, Pça. Rei 15, 08700 Igualada, Spain.

Encapsulation of DNA into hydroxyapatite (HAp) has been investigated using a rational approach that involves computer simulation and experimental techniques. The temporal evolution of the radial distribution functions derived from atomistic molecular dynamics simulations of Ca(2+), PO4(3-) and OH(-)-containing aqueous solutions in the presence and absence of B-DNA has been used to conclude that the backbone of the double helix acts as a template for HAp growth. More specifically, results reveal the formation of calcium phosphate clusters at the first stages of the simulations, which subsequently re-organize to nucleate HAp. This effect is produced in the absence and, especially, presence, of DNA indicating that the biomolecules do not inhibit but even promote mineral growth. Furthermore, computer simulations suggest that the diffusion of the OH(-) anions through the inorganic solution is the limiting step for the nucleation of the biomineral. Nanocapsules and crystalline nanorods of HAp containing DNA molecules inside have been prepared by mixing solutions containing Ca(2+) and PO4(3-) ions with fish sperm DNA at high pH. The dimensions and morphology of such nanostructures have been examined by transmission electron microscopy, while the characterization of the biomineral has been focused on the identification of DNA inside HAp using infrared, X-ray photoelectron and UV-vis spectroscopies, as well as gel electrophoresis. The biominerals reported in this work are important for biomedical applications requiring the protection of DNA from aggressive environmental conditions.
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http://dx.doi.org/10.1039/c3dt52112eDOI Listing
January 2014
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