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1.
Can J Public Health ; 114(6): 893-905, 2023 12.
Artigo em Inglês | MEDLINE | ID: mdl-37462842

RESUMO

OBJECTIVES: The overarching objective of this mixed methods longitudinal study was to understand whether and how rent subsidies and mentorship influenced socioeconomic inclusion outcomes for youth exiting homelessness. The focus of this paper is on the qualitative objectives, which evolved from a primary focus on exploring how study mentorship was working as a facilitator of socioeconomic inclusion to focusing on how participants navigated the hazy, liminal space between socioeconomic exclusion and inclusion. METHODS: This was a convergent mixed methods study scaffolded by community-based participatory action axiology. The quantitative component is reported elsewhere and involved a 2-year pilot randomized controlled trial where 24 participants received rent subsidies and 13 were randomly assigned a study mentor; proxy indicators of socioeconomic inclusion were measured every 6 months for 2.5 years. Qualitative objectives were explored using a qualitative descriptive design and theoretically framed using critical social theory. The lead author interviewed 12 participants every 6 months for 2.5 years. Qualitative interviews were analyzed using reflexive thematic analysis with an emphasis on critical interpretation. RESULTS: Navigating the liminal space between socioeconomic exclusion and inclusion was complex and non-linear, and the way youth navigated that journey was more strongly associated with factors like informal mentorship (naturally occurring "coach-like" mentorship) and identity capital (sense of purpose, control, self-efficacy, and self-esteem), rather than whether or not they were assigned a formal study mentor. CONCLUSION: A holistic approach integrating coaching and attention to identity capital alongside economic supports may be key to helping youth exiting homelessness achieve socioeconomic inclusion.


RéSUMé: OBJECTIFS: L'objectif primordial de cette étude longitudinale à méthodes mixtes était de comprendre si et comment les suppléments au loyer et le mentorat influencent les résultats sur le plan de l'inclusion socioéconomique pour les jeunes qui sortent du sans-abrisme. Notre article porte sur des objectifs qualitatifs; à l'origine, il visait principalement à explorer l'efficacité du mentorat des études comme moyen de faciliter l'inclusion socioéconomique, puis il a évolué en s'attachant à la manière dont les participantes et les participants trouvaient leurs repères dans l'espace liminaire flou entre l'exclusion et l'inclusion socioéconomique. MéTHODE: Cette étude à méthodes mixtes convergentes est échafaudée sur l'axiologie de l'action participative communautaire. L'élément quantitatif, qui fait l'objet d'un autre article, a impliqué un essai pilote comparatif randomisé de deux ans où 24 participantes et participants ont reçu des suppléments au loyer, et 13 ont été jumelés de façon aléatoire à un tuteur ou une tutrice scolaire; des indicateurs approximatifs de l'inclusion socioéconomique ont été mesurés tous les six mois pendant deux ans et demi. Les objectifs qualitatifs ont été explorés à l'aide d'un protocole descriptif qualitatif et encadrés théoriquement par la théorie sociale critique. L'autrice principale a interviewé 12 participantes et participants tous les six mois pendant deux ans et demi. Les entretiens qualitatifs ont été analysés en employant l'analyse thématique réflexive et en mettant l'accent sur l'interprétation critique. RéSULTATS: L'exploration de l'espace liminaire entre l'exclusion et l'inclusion socioéconomique était complexe et non linéaire, et le parcours des jeunes était davantage associé à des facteurs comme le mentorat informel (le mentorat naturel semblable à celui d'un entraîneur ou d'une entraîneuse) et le capital identitaire (le sentiment d'avoir un but, le contrôle, l'auto-efficacité et l'estime de soi) qu'au fait d'avoir ou non été jumelés à un tuteur ou une tutrice dans leurs études. CONCLUSION: Une démarche holistique intégrant l'encadrement et l'attention au capital identitaire, en plus des mesures de soutien économique, pourrait être essentielle pour aider les jeunes qui sortent du sans-abrisme à s'intégrer sur le plan socioéconomique.


Assuntos
Pessoas Mal Alojadas , Humanos , Adolescente , Estudos Longitudinais , Escuridão , Pesquisa Qualitativa , Fatores Socioeconômicos
2.
Med Clin North Am ; 107(1): 31-60, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36402499

RESUMO

Bipolar disorder is characterized by recurrent mood episodes, affecting 1% to 2% of the population. Although its defining features are manic and hypomanic episodes, its course is dominated by depressive syndromes. Diagnosis can be challenging owing to symptom overlap with other disorders. Management goals include early and complete remission of acute episodes and the prevention of relapse between episodes. We present an overview of bipolar disorder and its subtypes, including algorithms and suggestions for screening, assessment, and treatment.


Assuntos
Transtorno Bipolar , Humanos , Transtorno Bipolar/diagnóstico , Transtorno Bipolar/terapia , Transtorno Bipolar/epidemiologia , Escuridão , Recidiva
3.
J Am Med Inform Assoc ; 29(12): 2003-2013, 2022 11 14.
Artigo em Inglês | MEDLINE | ID: mdl-36166717

RESUMO

OBJECTIVE: To explore the use of a shared communication and coordination platform-the CareVirtue journal feature-for care networks of people living with Alzheimer's disease and related dementias to inform the design of care network support technologies. MATERIALS AND METHODS: In the primary study, care networks comprised the primary caregiver and other caregivers they invited to participate (eg, family members, in-home aides) used CareVirtue, for 60 days followed by a semistructured interview to explore primary caregivers' perceptions of usefulness. This secondary analysis focused on use of the shared journal feature of CareVirtue, which allowed care networks to communicate through posts that were shared with the network and to which network members could respond. Journal posts were analyzed using a deductive/inductive content analysis to categorize information behavior. We also conducted a thematic analysis of the interviews to identify primary caregivers' perceptions of the journal's usefulness. RESULTS: Care networks used the journal for: (1) information acquisition, (2) information sharing, (3) strategy development, and (4) information feedback. Thematic analysis revealed that caregivers felt the journal was useful at the individual, care network, and relational levels and that journal integration was influenced by care network structure and relationships. DISCUSSION: Care networks used the journal to document, share, and acquire information; co-create strategies; and provide support. The usefulness of this shared communication and coordination platform included individual and care network level benefits. CONCLUSION: These findings point to the importance of caregiver-centered technologies that support both the individual primary caregiver and the care network.


Assuntos
Doença de Alzheimer , Cuidadores , Humanos , Escuridão , Família , Comunicação
4.
Chemosphere ; 305: 135449, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-35750227

RESUMO

Behavioural disruptions are sensitive indicators of alterations to normal animal physiology and can be used for toxicity assessment. The small vertebrate zebrafish is a leading model organism for toxicological studies. The ability to continuously monitor the toxicity of drugs, pollutants, or environmental changes over several days in zebrafish can have high practical application. Although video-recordings can be used to monitor short-term zebrafish behaviour, it is challenging to videorecord prolonged experiments (e.g. circadian behaviour over several days) because of the darkness periods (nights) and the heavy data storage and image processing requirements. Alternatively, infrared-based activity monitors, widely used in invertebrate models such as drosophila, generate simple and low-storage data and could optimize large-scale prolonged behavioural experiments in zebrafish, thus favouring the implementation of high-throughput testing strategies. Here, we validate the use of a Locomotor Activity Monitor (LAM) to study the behaviour of zebrafish larvae, and we characterize the behavioural phenotypes induced by abnormal light conditions and by the Parkinsonian toxin MPP+. When zebrafish were deprived from daily light-cycle synchronization, the LAM detected various circadian disruptions, such as increased activity period, phase shifts, and decreased inter-daily stability. Zebrafish exposed to MPP+ (10, 100, 500 µM) showed a concentration-dependent decrease in activity, sleep disruptions, impaired habituation to repetitive startles (visual-motor responses), and a slower recovery to normal activity after the startle-associated stress. These phenotypes evidence the feasibility of using infrared-based LAM to assess multi-parameter behavioural disruptions in zebrafish. The procedures in this study have wide applicability and may yield standard methods for toxicity testing.


Assuntos
Ritmo Circadiano , Peixe-Zebra , Animais , Ritmo Circadiano/genética , Escuridão , Fotoperíodo , Sono , Peixe-Zebra/fisiologia
5.
Artigo em Inglês | MEDLINE | ID: mdl-34501660

RESUMO

(1) Measuring personal exposure to solar ultraviolet radiation (UVR) poses a major challenges for researchers. Often, the study design determines the measuring devices that can be used, be it the duration of measurements or size restrictions on different body parts. It is therefore of great importance that measuring devices produce comparable results despite technical differences and modes of operation. Particularly when measurement results from different studies dealing with personal UV exposure are to be compared with each other, the need for intercomparability and intercalibration factors between different measurement systems becomes significant. (2) Three commonly used dosimeter types-(polysulphone film (PSF), biological, and electronic dosimeters)-were selected to perform intercalibration measurements. They differ in measurement principle and sensitivity, measurement accuracy, and susceptibility to inaccuracies. The aim was to derive intercalibration factors for these dosimeter types. (3) While a calibration factor between PSF and electronic dosimeters of about 1.3 could be derived for direct irradiation of the dosimeters, this was not the case for larger angles of incidence of solar radiation with increasing fractions of diffuse irradiation. Electronic dosimeters show small standard deviation across all measurements. For biological dosimeters, no intercalibration factor could be found with respect to PSF and electronic dosimeters. In a use case, the relation between steady-state measurements and personal measurements was studied. On average, persons acquired only a small fraction of the ambient radiation.


Assuntos
Dosímetros de Radiação , Raios Ultravioleta , Escuridão , Eletrônica , Doses de Radiação
6.
J Oleo Sci ; 69(10): 1163-1179, 2020 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-32908089

RESUMO

Sixty-four bottles of red palm olein and palm olein (constituted as control) samples were stored at permutations of common home setting variables which are: temperature (room temperature (24°C) or 8°C), light (kept in dark or exposure under light) and oxygen (opened or sealed caps). The effects of temperature, oxygen and light on the stability of red palm olein and palm olein were studied over 4 months of storage at simulated domestic conditions. The degree of auto- and photo-oxidations was evaluated by monitoring the following quality parameters: acidity, peroxide and p-anisidine values, fatty acids composition, carotenes and vitamin E. It is noted from the study that opened bottles of red palm olein was found to be stable for 4 months in comparison to its counterpart (palm olein) evidenced from their primary oxidative constituents (peroxides) and hydrolytic behavior (free fatty acids). Opened bottles are better off when stored at 8°C and protected from light for a longer shelf-life. Sealed bottles of palm olein showed better storage stability in the dark at 8°C; whereas sealed bottles of red palm olein was found to be stable at both temperatures studied without the influence of light. After 4 months of varying storage conditions, the fatty acid composition, vitamin E and carotenes of both oils remained unchanged. The phytonutrients in red palm olein rendered better storage stability when compared to palm olein.


Assuntos
Temperatura Baixa , Escuridão , Armazenamento de Alimentos , Óleo de Palmeira/química , Compostos de Anilina/análise , Carotenoides/análise , Ácidos Graxos/análise , Qualidade dos Alimentos , Luz/efeitos adversos , Oxirredução , Oxigênio/efeitos adversos , Óleo de Palmeira/classificação , Peróxidos , Fotólise , Vitamina E/análise
7.
Accid Anal Prev ; 146: 105731, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32827843

RESUMO

The effect of ambient light level on road traffic collisions (RTCs) involving a motorcycle was investigated. Data were drawn from the STATS19 database of UK reported RTCs for the period 2005-2015. To isolate the effect of ambient light (daylight vs darkness) an odds ratio was used to compare RTCs at specific times of day in the weeks either side of the Spring and Autumn clock changes. This work extended previous studies by using a more precise method for distinguishing between RTCs in daylight and after dark, thus avoiding the ambiguity of twilight. Data for four-wheel motor vehicle (FWMV) RTCs were also investigated to provide a datum. As expected, the risk of an RTC occurring was significantly higher after dark compared to daylight for both motorcycles and FWMVs. Investigation of contextual factors suggests that risk after dark is significantly higher for motorcycles compared to FWMVs for RTCs with two-vehicles, on roads with low speed limits (≤30 mph), at T-junctions, and junctions controlled by a give way sign. These are the situations where visual aids for increasing conspicuity after dark have the greater potential for reducing motorcycle RTCs.


Assuntos
Acidentes de Trânsito/estatística & dados numéricos , Motocicletas , Adulto , Estudos de Casos e Controles , Escuridão , Bases de Dados Factuais , Feminino , Humanos , Masculino , Razão de Chances , Medição de Risco
8.
Environ Health ; 19(1): 74, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32611430

RESUMO

BACKGROUND: Research has suggested that artificial light at night (LAN) may disrupt circadian rhythms, sleep, and contribute to the development of obesity. However, almost all previous studies are cross-sectional, thus, there is a need for prospective investigations of the association between LAN and obesity risk. The goal of our current study was to examine the association between baseline LAN and the development of obesity over follow-up in a large cohort of American adults. METHODS: The study included a sample of 239,781 men and women (aged 50-71) from the NIH-AARP Diet and Health Study who were not obese at baseline (1995-1996). We used multiple logistic regression to examine whether LAN at baseline was associated with the odds of developing obesity at follow-up (2004-2006). Outdoor LAN exposure was estimated from satellite imagery and obesity was measured based on self-reported weight and height. RESULTS: We found that higher outdoor LAN at baseline was associated with higher odds of developing obesity over 10 years. Compared with the lowest quintile of LAN, the highest quintile was associated with 12% and 19% higher odds of developing obesity at follow-up in men (OR (95% CI) = 1.12 (1.00, 1.250)) and women (1.19 (1.04, 1.36)), respectively. CONCLUSIONS: Our findings suggest that high LAN exposure could predict a higher risk of developing obesity in middle-to-older aged American adults.


Assuntos
Escuridão/efeitos adversos , Escolaridade , Iluminação , Obesidade/epidemiologia , Sono , Fatores Socioeconômicos , Idoso , Feminino , Humanos , Luz , Masculino , Pessoa de Meia-Idade , Obesidade/etiologia , Pobreza , Estudos Prospectivos , Fatores de Risco , Fatores de Tempo , Estados Unidos/epidemiologia
11.
PLoS One ; 13(1): e0189931, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29304108

RESUMO

Behavioral states alternate between wakefulness (wk), rapid eye movement (rem) and non-rem (nrem) sleep at time scale of hours i.e., light and dark cycle rhythms and from several tens of minutes to seconds (i.e., brief awakenings during sleep). Using statistical analysis of bout duration, Markov chains of sleep-wk dynamics and quantitative EEG analysis, we evaluated the influence of light/dark (ld) changes on brain function along the sleep-wk cycle. Bout duration (bd) histograms and Kaplan-Meier (km) survival curves of wk showed a bimodal statistical distribution, suggesting that two types of wk do exist: brief-wk (wkb) and long-wk (wkl). Light changes modulated specifically wkl bouts, increasing its duration during active/dark period. In contrast, wkb, nrem and rem bd histograms and km curves did not change significantly along ld cycle. Hippocampal eeg of both types of wk were different: in comparison wkb showed a lower spectral power in fast gamma and fast theta bands and less emg tone. After fitting a four-states Markov chain to mice hypnograms, moreover in states transition probabilities matrix was found that: in dark/active period, state-maintenance probability of wkl increased, and probability of wkl to nrem transition decreased; the opposite was found in light period, favoring the hypothesis of the participation of brief wk into nrem-rem intrinsic sleep cycle, and the role of wkl in SWS homeostasis. In conclusion, we propose an extended Markov model of sleep using four stages (wkl, nrem, rem, wkb) as a fully adequate model accounting for both modulation of sleep-wake dynamics based on the differential regulation of long-wk (high gamma/theta) epochs during dark and light phases.


Assuntos
Escuridão , Luz , Sono/fisiologia , Vigília/fisiologia , Animais , Eletroencefalografia , Masculino , Cadeias de Markov , Camundongos , Camundongos Endogâmicos C57BL
15.
Biophys J ; 111(4): 883-891, 2016 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-27558731

RESUMO

Circadian rhythms are endogenously generated daily oscillations in physiology that are found in all kingdoms of life. Experimental studies have shown that the fitness of Synechococcus elongatus, a photosynthetic microorganism, is severely affected in non-24-h environments. However, it has been difficult to study the effects of clock-environment mismatch on cellular physiology because such measurements require a precise determination of both clock state and growth rate in the same cell. Here, we designed a microscopy platform that allows us to expose cyanobacterial cells to pulses of light and dark while quantitatively measuring their growth, division rate, and circadian clock state over many days. Our measurements reveal that decreased fitness can result from a catastrophic growth arrest caused by unexpected darkness in a small subset of cells with incorrect clock times corresponding to the subjective morning. We find that the clock generates rhythms in the instantaneous growth rate of the cell, and that the time of darkness vulnerability coincides with the time of most rapid growth. Thus, the clock mediates a fundamental trade-off between growth and starvation tolerance in cycling environments. By measuring the response of the circadian rhythm to dark pulses of varying lengths, we constrain a mathematical model of a population's fitness under arbitrary light/dark schedules. This model predicts that the circadian clock is only advantageous in highly regular cycling environments with frequencies sufficiently close to the natural frequency of the clock.


Assuntos
Relógios Circadianos , Meio Ambiente , Synechococcus/citologia , Proliferação de Células/efeitos da radiação , Relógios Circadianos/efeitos da radiação , Escuridão , Modelos Biológicos , Synechococcus/efeitos da radiação
16.
Appl Environ Microbiol ; 82(14): 4180-4189, 2016 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-27208121

RESUMO

UNLABELLED: Investigating the physiology of cyanobacteria cultured under a diel light regime is relevant for a better understanding of the resulting growth characteristics and for specific biotechnological applications that are foreseen for these photosynthetic organisms. Here, we present the results of a multiomics study of the model cyanobacterium Synechocystis sp. strain PCC 6803, cultured in a lab-scale photobioreactor in physiological conditions relevant for large-scale culturing. The culture was sparged with N2 and CO2, leading to an anoxic environment during the dark period. Growth followed the availability of light. Metabolite analysis performed with (1)H nuclear magnetic resonance analysis showed that amino acids involved in nitrogen and sulfur assimilation showed elevated levels in the light. Most protein levels, analyzed through mass spectrometry, remained rather stable. However, several high-light-response proteins and stress-response proteins showed distinct changes at the onset of the light period. Microarray-based transcript analysis found common patterns of ∼56% of the transcriptome following the diel regime. These oscillating transcripts could be grouped coarsely into genes that were upregulated and downregulated in the dark period. The accumulated glycogen was degraded in the anaerobic environment in the dark. A small part was degraded gradually, reflecting basic maintenance requirements of the cells in darkness. Surprisingly, the largest part was degraded rapidly in a short time span at the end of the dark period. This degradation could allow rapid formation of metabolic intermediates at the end of the dark period, preparing the cells for the resumption of growth at the start of the light period. IMPORTANCE: Industrial-scale biotechnological applications are anticipated for cyanobacteria. We simulated large-scale high-cell-density culturing of Synechocystis sp. PCC 6803 under a diel light regime in a lab-scale photobioreactor. In BG-11 medium, Synechocystis grew only in the light. Metabolite analysis grouped the collected samples according to the light and dark conditions. Proteome analysis suggested that the majority of enzyme-activity regulation was not hierarchical but rather occurred through enzyme activity regulation. An abrupt light-on condition induced high-light-stress proteins. Transcript analysis showed distinct patterns for the light and dark periods. Glycogen gradually accumulated in the light and was rapidly consumed in the last quarter of the dark period. This suggests that the circadian clock primed the cellular machinery for immediate resumption of growth in the light.


Assuntos
Dióxido de Carbono/metabolismo , Escuridão , Glicogênio/metabolismo , Luz , Nitrogênio/metabolismo , Synechocystis/crescimento & desenvolvimento , Synechocystis/metabolismo , Aerobiose , Anaerobiose , Proteínas de Bactérias/análise , Perfilação da Expressão Gênica , Espectrometria de Massas , Análise em Microsséries , Fotobiorreatores/microbiologia , Synechocystis/química
17.
J Toxicol Environ Health A ; 79(7): 307-19, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27029512

RESUMO

Artificial light at night (ALAN), producing light pollution (LP), is not a matter restricted to astronomy anymore. Light is part of modern societies and, as a consequence, the natural cycle day-night (bright-dark) has been interrupted in a large segment of the global population. There is increasing evidence that exposure to certain types of light at night and beyond threshold levels may produce hazardous effects to humans and the environment. The concept of "dark skies reserves" is a step forward in order to preserve the night sky and a means of enhancing public awareness of the problem of spread of light pollution worldwide. The aim of this study was to assess the skyglow at two sites in Portugal, the Peneda-Gerês National Park (PNPG) and the region now known as Dark Sky Alqueva Reserve. The latter site was classified as a "Starlight Tourism Destination" by the Starlight Foundation (the first in the world to achieve this classification) following a series of night sky measurements in situ described herein. The measurements at PNPG also contributed to the new set of regulations concerning light pollution at this national park. This study presents the first in situ systematic measurements of night sky brightness, showing that at the two sites the skies are mostly in levels 3 to 4 of the Bortle 9-level scale (with level 1 being the best achievable). The results indicate that the sources of light pollution and skyglow can be attributed predominantly to contamination from nearby urban regions.


Assuntos
Escuridão , Monitoramento Ambiental , Poluição Ambiental/análise , Iluminação , Humanos , Parques Recreativos , Portugal
18.
PLoS One ; 11(2): e0150164, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26915030

RESUMO

A new operant test for preclinical pain research, termed the Mechanical Conflict System (MCS), is presented. Rats were given a choice either to remain in a brightly lit compartment or to escape to a dark compartment by crossing an array of height-adjustable nociceptive probes. Latency to escape the light compartment was evaluated with varying probe heights (0, .5, 1, 2, 3, and 4 mm above compartment floor) in rats with neuropathic pain induced by constriction nerve injury (CCI) and in naive control rats. Escape responses in CCI rats were assessed following intraperitoneal administration of pregabalin (10 and 30 mg/kg), morphine (2.5 and 5 mg/kg), and the tachykinin NK1 receptor antagonist, RP 67580 (1 and 10 mg/kg). Results indicate that escape latency increased as a function of probe height in both naive and CCI rats. Pregabalin (10 and 30 mg/kg) and morphine (5 mg/kg), but not RP 67580, decreased latency to escape in CCI rats suggesting an antinociceptive effect. In contrast, morphine (10 mg/kg) but not pregabalin (30 mg/kg) increased escape latency in naive rats suggesting a possible anxiolytic action of morphine in response to light-induced fear. No order effects following multiple test sessions were observed. We conclude that the MCS is a valid method to assess behavioral signs of affective pain in rodents.


Assuntos
Aprendizagem da Esquiva/fisiologia , Condicionamento Operante , Conflito Psicológico , Reação de Fuga/fisiologia , Etologia/instrumentação , Traumatismos do Pé/fisiopatologia , Hiperalgesia/fisiopatologia , Dor Nociceptiva/fisiopatologia , Analgésicos/administração & dosagem , Analgésicos/uso terapêutico , Animais , Ansiolíticos/administração & dosagem , Ansiolíticos/uso terapêutico , Comportamento de Escolha , Condicionamento Operante/fisiologia , Escuridão , Relação Dose-Resposta a Droga , Medo , Traumatismos do Pé/psicologia , Hiperalgesia/etiologia , Hiperalgesia/psicologia , Injeções Intraperitoneais , Isoindóis/administração & dosagem , Isoindóis/uso terapêutico , Ligadura , Luz/efeitos adversos , Masculino , Morfina/administração & dosagem , Morfina/uso terapêutico , Neuralgia/tratamento farmacológico , Neuralgia/etiologia , Neuralgia/fisiopatologia , Antagonistas dos Receptores de Neurocinina-1/administração & dosagem , Antagonistas dos Receptores de Neurocinina-1/uso terapêutico , Dor Nociceptiva/tratamento farmacológico , Dor Nociceptiva/psicologia , Pregabalina/administração & dosagem , Pregabalina/uso terapêutico , Ratos , Ratos Sprague-Dawley , Tempo de Reação/efeitos dos fármacos , Nervo Isquiático/lesões , Nervo Isquiático/fisiopatologia
19.
J Endod ; 40(8): 1235-40, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25069940

RESUMO

INTRODUCTION: Dental discoloration with use of materials containing bismuth oxide has been reported. It is postulated that the discoloration is a result of chemical interaction of bismuth oxide with dentin. The aim of the study was to analyze dental color alteration and the chemical interaction of bismuth oxide with the main components present in composite (methacrylate) and in dentin (collagen). METHODS: Fifty bovine teeth were prepared and filled with white mineral trioxide aggregate (MTA) Angelus, Portland cement (PC) with 20% zirconium oxide, or PC with 20% calcium tungstate and then sealed with composite. Triple antibiotic paste and unfilled samples were the positive and negative controls, respectively. The specimens were stored in separate flasks immersed in tap water at 37°C with ambient light blocked out. The color assessment was performed with a spectrophotometer at different intervals, namely before filling and 24 hours, 15 days, and 30 days after filling. The color change and the luminosity were calculated. The statistical analysis was performed by using nonparametric Kruskal-Wallis and Dunn tests (P < .05). The interaction of the bismuth oxide, zirconium oxide, and calcium tungstate with collagen and methacrylate was assessed by placing the materials in contact, followed by color assessment. RESULTS: The analysis of color change values showed that all the materials presented color alteration after the evaluated periods. Statistically higher luminosity was verified for PC/20% zirconium oxide in comparison with white MTA Angelus (P < .05). The teeth filled with white MTA Angelus demonstrated a grayish discoloration with evident dentin staining. Bismuth oxide exhibited a color change when in contact with collagen. CONCLUSIONS: The color of white MTA Angelus was altered in contact with dental structures. Collagen, which is present in dentin matrix, reacted with bismuth oxide, resulting in a grayish discoloration. The use of an alternative radiopacifier to replace bismuth in white MTA is indicated.


Assuntos
Bismuto/farmacologia , Cimentos Dentários/farmacologia , Dentina/efeitos dos fármacos , Óxidos/farmacologia , Materiais Restauradores do Canal Radicular/farmacologia , Descoloração de Dente/induzido quimicamente , Animais , Bismuto/química , Compostos de Cálcio/química , Compostos de Cálcio/farmacologia , Bovinos , Colágeno/efeitos dos fármacos , Cor , Resinas Compostas/química , Escuridão , Materiais Dentários/química , Teste de Materiais , Metacrilatos/química , Distribuição Aleatória , Silicatos/química , Silicatos/farmacologia , Espectrofotometria/instrumentação , Temperatura , Fatores de Tempo , Compostos de Tungstênio/química , Compostos de Tungstênio/farmacologia , Água/química , Zircônio/química , Zircônio/farmacologia
20.
PLoS One ; 7(11): e49593, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-23152925

RESUMO

Förster resonance energy transfer (FRET) microscopy is widely used to study protein interactions in living cells. Typically, spectral variants of the Green Fluorescent Protein (FPs) are incorporated into proteins expressed in cells, and FRET between donor and acceptor FPs is assayed. As appreciable FRET occurs only when donors and acceptors are within 10 nm of each other, the presence of FRET can be indicative of aggregation that may denote association of interacting species. By monitoring the excited-state (fluorescence) decay of the donor in the presence and absence of acceptors, dual-component decay analysis has been used to reveal the fraction of donors that are FRET positive (i.e., in aggregates)._However, control experiments using constructs containing both a donor and an acceptor FP on the same protein repeatedly indicate that a large fraction of these donors are FRET negative, thus rendering the interpretation of dual-component analysis for aggregates between separately donor-containing and acceptor-containing proteins problematic. Using Monte-Carlo simulations and analytical expressions, two possible sources for such anomalous behavior are explored: 1) conformational heterogeneity of the proteins, such that variations in the distance separating donor and acceptor FPs and/or their relative orientations persist on time-scales long in comparison with the excited-state lifetime, and 2) FP dark states.


Assuntos
Escuridão , Transferência Ressonante de Energia de Fluorescência , Proteínas de Fluorescência Verde/metabolismo , Simulação por Computador , Método de Monte Carlo
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