Publications by authors named "M K S Silva"

10,883 Publications

Salivary parameters alterations after early exposure to environmental methylmercury: A preclinical study in offspring rats.

J Trace Elem Med Biol 2021 Jul 16;68:126820. Epub 2021 Jul 16.

Laboratory of Functional and Structural Biology, Institute of Biological Sciences, Federal University of Para, Belém, PA, Brazil. Electronic address:

Background: Methylmercury (MeHg) is still considered a global pollutant of major concern; thus, it becomes relevant to investigate and validate alternative diagnostic methods to track early-life human exposure. This study aimed to evaluate the salivary parameters and to characterize potential mechanisms of oxidative damage on the salivary glands (SG) of offspring rats after pre- and postnatal environmental-experimental MeHg exposure.

Methods: Pregnant Wistar rats were daily exposed to 40 μg/kg MeHg during both gestational and lactation periods. Then, the saliva of offspring rats was analyzed in terms of flow rate, amylase activity, and total protein concentration. The SG of the offspring rats were dissected to perform the oxidative biochemistry analyses of antioxidant capacity against peroxyl radicals (ACAP), lipid peroxidation (LPO), and nitrite levels.

Results: Exposure to MeHg significantly decreased the ACAP, increased LPO and nitrite levels, decreased salivary flow rate, amylase activity, and total protein concentration.

Conclusion: Saliva analyses can predict damages induced by early-life MeHg exposure and may be used as an auxiliary diagnostic method.
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http://dx.doi.org/10.1016/j.jtemb.2021.126820DOI Listing
July 2021

Neurochemical abnormalities in the hippocampus of male rats displaying audiogenic seizures, a genetic model of epilepsy.

Neurosci Lett 2021 Jul 19:136123. Epub 2021 Jul 19.

Laboratório de Neurofarmacologia, Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais. Av Antonio Carlos 6627, Campus Pampulha, CEP 30190-901, Belo Horizonte, MG, Brazil. Electronic address:

Background: Epilepsy is a disorder characterized by recurrent seizures that affects 1% of the population. However, the neurochemical alterations observed in epilepsy are not fully understood. There are different animal models of epilepsy, such as genetic or drug induced. In the present study, we utilize Wistar Audiogenic Rats (WAR), a murine strain that develops seizures in response to high intensity audio stimulation, in order to investigate abnormalities in glutamatergic and GABAergic systems.

Methods: Synaptosomes and glial plasmalemmal vesicles were prepared from hippocampus and cortex, respectively. Glutamate and GABA release and uptake were assayed by monitoring the fluorescence and using L-[H]-radiolabeled compounds. Glutamate and calcium concentration in the synaptosomes were also measured. The expression of neuronal calcium sensor 1 (NCS-1) was determined by western blot.

Results: Glutamate and GABA release evoked by KCl was decreased in WAR compared to control Wistar rats. Calcium independent release was not considerably different in both groups. The total amount of glutamate of synaptosomes, as well as glutamate uptake by synaptosomes and GPV were also decreased in WAR in comparison with the controls. In addition, [Ca] of hippocampal synaptosomes, as well as NCS-1 expression in the hippocampus, were increased in WAR in comparison with controls.

Conclusion: In conclusion, our results suggest that WAR have important alterations in the glutamatergic and GABAergic pathways, as well as an increased expression of NCS-1 in the hippocampus and inferior colliculus. These alterations may be linked to the spreading of hyperexcitability and recruitment of various brain regions.
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http://dx.doi.org/10.1016/j.neulet.2021.136123DOI Listing
July 2021

Increased PD-1 Level in Severe Cervical Injury Is Associated With the Rare Programmed Cell Death 1 () rs36084323 A Allele in a Dominant Model.

Front Cell Infect Microbiol 2021 1;11:587932. Epub 2021 Jul 1.

Laboratory of Immunogenetics, Department of Immunology, Aggeu Magalhães Institute, Oswaldo Cruz Foundation, Recife, Brazil.

The high-risk oncogenic human papillomavirus (HPV) has developed mechanisms for evasion of the immune system, favoring the persistence of the infection. The chronic inflammation further contributes to the progression of tissue injury to cervical cancer. The programmed cell death protein (PD-1) after contacting with its ligands (PD-L1 and PD-L2) exerts an inhibitory effect on the cellular immune response, maintaining the balance between activation, tolerance, and immune cell-dependent lesion. We evaluated 295 patients exhibiting or not HPV infection, stratified according to the location (injured and adjacent non-injured areas) and severity of the lesion (benign, pre-malignant lesions). Additionally, we investigated the role of the promoter region -606G>A polymorphism (rs36084323) on the studied variables. PD-1 and expression were evaluated by immunohistochemistry and qPCR, respectively, and the polymorphism was evaluated by nucleotide sequencing. Irrespective of the severity of the lesion, PD-1 levels were increased compared to adjacent uninjured areas. Additionally, in cervical intraepithelial neoplasia (CIN) I, the presence of HPV was associated with increased ( = 0.0649), whereas in CIN III was associated with decreased ( = 0.0148) PD-1 levels, compared to the uninjured area in absence of HPV infection. The -606A allele was rare in our population (8.7%) and was not associated with the risk for development of HPV infection, cytological and histological features, and aneuploidy. In contrast, irrespective of the severity of the lesion, patients exhibiting the mutant -606A allele at single or double doses exhibited increased protein and gene expression when compared to the -606GG wild type genotype. Besides, the presence of HPV was associated with the decrease in expression and PD-1 levels in carriers of the -606 A allele presenting severe lesions, suggesting that other mediators induced during the HPV infection progression may play an additional role. This study showed that increased PD-1 levels are influenced by the -606G>A nucleotide variation, particularly in low-grade lesions, in which the A allele favors increased expression, contributing to HPV immune system evasion, and in the high-grade lesion, by decreasing tissue PD-1 levels.
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http://dx.doi.org/10.3389/fcimb.2021.587932DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8288189PMC
July 2021

Analysis of infection rates and duration of short and long-term hemodialysis catheters in a teaching hospital.

J Vasc Bras 2020 14;19:e20190142. Epub 2020 Sep 14.

Associação de Integração Social de Itajubá - AISI, Hospital de Clínicas de Itajubá - HCI, Departamento de Cirurgia Vascular e Endovascular, Itajubá, MG, Brasil.

Background: Short-term (ST) and long-term tunneled (LTT) central venous catheters for hemodialysis (CVCH) are critical for hemodialysis therapy. However, few studies have been conducted in Brazil to investigate the incidence of complications with these two types of catheters.

Objectives: To analyze complications and duration of CVCH in a hemodialysis center at a teaching hospital.

Methods: Single-center, longitudinal, and retrospective study of 115 consecutive patients undergoing hemodialysis catheter placement (67 ST and 48 LTT) over a 2-year period, analyzing overall survival, patency, loss of access, and incidence of complications.

Results: Sixty percent of the patients were male and mean age was 62 years. The most common puncture site was the right internal jugular vein. Systemic arterial hypertension was present in 95% of cases. Median catheter in-place duration was 50 days (ST) vs. 112 days (LTT; p < 0.0001). There was no difference in overall survival. Incidence of catheter-related infection was higher in ST CVCH, with sp. the microorganism most often found. The infection rate per 1000 days was higher in ST than in LTT catheters (16.7 events/1000 days vs. 7.0 events/1000 days). Low income was the only factor related to higher incidence of infection.

Conclusions: The in-place duration of long-term catheters was significantly longer compared to short-term CVCH, but still below the values reported in the literature and without impact on overall survival. Low income was a factor associated with catheter infection.
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http://dx.doi.org/10.1590/1677-5449.190142DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8276652PMC
September 2020

Chondroitin sulfate from fish waste exhibits strong intracellular antioxidant potential.

Braz J Med Biol Res 2021 16;54(10):e10730. Epub 2021 Jul 16.

Programa de Pós-Graduação em Bioquímica e Biologia Molecular, Departamento de Bioquímica, Universidade Federal do Rio Grande do Norte, Natal, RN, Brasil.

Chondroitin sulfate (CS) is a type of glycosaminoglycan described as an antioxidant molecule that has been found in animal species such as fish. Tilapia (Oreochromis niloticus) represents an eco-friendly source of this compound, since its economical processing generates usable waste, reducing the negative environmental impact. This waste was used for CS extraction, purification, characterization by enzymatic degradation, and evaluation of its antioxidant effect. CS obtained from tilapia presented sulfation mainly at carbon 4 of galactosamine, and it was not cytotoxic at concentrations up to 200 µg/mL. Furthermore, 100 µg/mL of CS from tilapia reduced the levels of reactive oxygen species to 47% of the total intracellular reactive oxygen species level. The ability of CS to chelate metal ions in vitro also suggested an ability to react with other pathways that generate oxidative radicals, such as the Haber-Weiss reaction, acting intracellularly in more than one way. Although the role of CS from tilapia remains unclear, the pharmacological effects described herein indicate that CS is a potential molecule for further study of the relationship between the structures and functions of chondroitin sulfates as antioxidants.
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http://dx.doi.org/10.1590/1414-431X2020e10730DOI Listing
July 2021